Where is Driftwood Johnson when you need him?
Well, I wasn't going to reply because everything has already pretty much been said.
But since you asked...........
I have owned all of them. Uberti Cattleman, Colt Single Action Army, Ruger 'original model' Vaquero and New Vaquero, Ruger Blackhawk and Ruger Three Screw Blackhawks.
It's all been said. The Uberti is very similar to the original Colt design. The parts are not interchangeable, but they work exactly the same.
The 'original model' Vaquero and the New Vaquero mechanisms are completely different. Ruger replaced all the old leaf type springs with coil springs way back in the 1950s with the old Three Screw Blackhawks.
2nd Gen Colt Single Action Army. I replaced the bolt/trigger spring with a modern wire spring, everything else is leaf springs. Take an Uberti apart and it will look pretty much exactly the same.
Ruger Three Screw Flat Top 44 Magnum. No leaf springs, everything is coil springs. Because the coil springs each need a plunger to do their job, the part count went up. But it operates exactly like a Colt, loads from half cock and is not safe to carry with a live round under the chamber.
Sometime in the mid 1970s Ruger redesigned their line of single action revolvers. This was because they were on the losing end of a couple of expensive lawsuits when idiots who did not understand not to leave a live round under the hammer shot themselves or caused grievous injury. So Ruger completely redesigned their entire line of single action revolvers to include a Transfer Bar. With the Transfer Bar these guns became completely safe to carry fully loaded with six rounds because the Transfer Bar was not in position to 'transfer' the energy from the hammer to the frame mounted firing pin unless the trigger had been pulled back.
Here is my old 45 Colt/45 ACP Blackhawk that I bought in 1975. Notice there are no longer three screws in the frame, but two pins instead.
The 'original model' Vaquero was nothing more than a New Model (as Ruger calls them) Blackhawk without the adjustable sights and the frame was rounded over to look more like a SAA. They were built on the same large frame as the Blackhawks, so they could take the same 44 Magnum loads that a 44 Magnum Blackhawk could. Made from 1993 until 2005. I bought this 45 Colt 'original model' Vaquero used around 2000 when I first started shooting cowboy. My notes say it was made in 1994.
In 2005 Ruger introduced the New Vaquero. (Don't confuse that with New Model Rugers. New Model refers to the fact they have transfer bars inside. All modern Ruger single actions are New Models whether or not they have 'New' in the model name or not. Yeah, New Vaquero was a dumb choice of names.) The 'original model' Vaquero was considerably larger than the old Single Action Army. This was why it could take 44 Magnum loads, because the cylinder was larger and had more metal surrounding the chambers than the old Colts.
All three cylinders in this photo are chambered for 45 Colt. You can see how much more massive the 'original model' Vaquero cylinder in the center is than the Uberti Cattleman cylinder on the left or the 2nd Gen Colt cylinder on the right. Notice too how much more metal surrounds each chamber.
Anyway, in 2005 Ruger discontinued the 'original model' Vaquero and replaced it with the New Vaquero. At the top of this photo is that same 45 Colt 'original model' Vaquero, at the bottom is a 357 Magnum New Vaquero. You may or may not be able to detect the difference in size. There were several other features of the New Vaquero that made it more similar in appearance to the Colt SAA. With the 'original model' the hammer spur was shorter. You could sight the gun with the hammer down. The New Vaquero featured a taller hammer spur more in keeping with the shape of a SAA hammer. Just like with a Colt, you cannot sight the gun with the hammer down, the taller hammer spur blocks the sights. Not a big deal with a single action revolver, you can't fire it with the hammer down anyway. There are other hammers available for the New Vaquero now, but that is the way they first came. The ejector rod handle on the New Vaquero looked a little bit more like the one on a SAA, but not much. The cylinder pin on the New Vaquero was shorter. With the Blackhawk and 'original model' Vaquero you could not remove the cylinder pin from the gun without first removing the ejector housing. With a New Vaquero you can pop it right out, just like a Colt, and you can lose it in the grass just as easily. For some reason, the grips on the New Vaquero are much thinner and less handfilling than on the older model. I don't know why.
Here is a good size comparison of a New Vaquero and a 2nd Gen Colt. Can you guess which one is which? Even though they are almost the same size, I believe the Ruger weighs a tad more than the Colt. Don't really remember right now.
Here is a comparison of the New Vaquero cylinder on the left, and the 2nd Gen Colt cylinder on the right. Darn close in all dimensions. I don't remember off the top of my head right now, I did a bunch of measurements at the time, but I dunno what I did with the results. Anyway, this is why the New Vaquero is not chambered for 44 Magnum.
Ruger New Vaquero torn down. Yes, lots and lots of parts. Because of the addition of the Transfer Bar in the 1970s. The vertical piece attached to the trigger is the Transfer Bar. Yes, trickier to take apart than a Colt (or an Uberti) but not impossible. The trickiest part is getting the transfer bar/trigger assembly back in at the same time as the hammer/hand assembly. There are plenty of instructions and videos on the web to help with that. Wish they had existed the first time I took one apart.
Uberti Cattleman. I have owned two of these. The first was a piece of doo-doo. Worst trigger pull of any revolver I have ever owned. And the barrel was not screwed on correctly, the front sight leaned noticeably to one side. I got rid of it pretty quickly. This one is a lot better, I still have it. Not the quality of a Colt, but not the price tag either.
OK, so what's the deal with coil springs vs leaf springs? Here is a broken trigger/bolt spring from a 2nd Gen Colt. Very common. The metal can develop microscopic stress fractures at the base of the legs. Over time they can get worse, and eventually fail like this. THIS IS NOT GUARANTEED TO HAPPEN EVERY TIME. I have Colts over 100 years old with their original springs and they are still fine. But this is why Bill Ruger got rid of leaf springs and replaced them with
almost indestructible coil springs.
This photo shows a modern wire trigger/bolt spring that I installed in that Uberti Cattleman. Takes away the problem of the spring ever breaking. One of my 2nd Gens has this spring in it, one does not. Just something you can add to increase the reliability.
So. Uberti, only safe when loaded with five rounds.
Vaquero completely safe loaded with six rounds.
Just so you know, I follow the rule with my Colts and only load them with five rounds. Not a big deal. There is a sequence to doing this correctly that we can talk about at another time. This is the reason that everybody in CAS is required to load only five rounds in their pistols, no matter what brand they are shooting. And as John Wayne said, if you think you're going to need six, load six.
Built like a Tank. You will hear Rugers described that way all the time. As we have seen, the frame and cylinder are no bigger with a Ruger than with a Colt, or Uberti. But the cross sections of the internal parts are greater with the Rugers, and I believe the parts will withstand more abuse. But treat it right, and a Colt or Uberti will last 100 years.
Special Note: you will hear in many places that a 45 Colt New Vaquero is strong enough to withstand ammunition loaded to higher pressures than the SAAMI max pressure for the cartridge. I will not comment on that other than to say that Ruger does not recommend it.
One more photo. These are the lock parts of a Colt. Uberti parts will be very similar. The arrows point to why one should never load one of these with six rounds. The lower arrow points to the tip of the trigger, called the sear. The upper arrow points to the so called 'safety cock notch' on the hammer. The supposedly safe way to carry a Colt was to ease the hammer back until the sear popped into the 'safety cock' notch. Then the firing pin could not strike the primer of a round in the chamber. Notice how thin the sear is. Imagine what would happen if the gun fell to the ground and landed on the hammer spur. There is an excellent chance the sear would snap off, or the overhanging lip of the 'safety cock' notch would shear off. Either way, the gun would fire. And who knows where it would be pointing at the time.
You can also see in this photo the leaf spring attached to the hand. Probably the most common spring in a Colt to break, even more common than the split trigger/bolt spring. These days though, Uberti has replaced this leaf spring with a coil spring mounted in the frame, very similar to the arrangement that Ruger uses.
One more thing. Uberti recently released a new design for the hammer with their single action revolvers. In the new design, the firing pin is normally retracted into the hammer and cannot reach the primer of a round in the chamber. When the trigger is pulled, an actuator shoves the firing pin forward so it can strike the primer. When the trigger is released, the firing pin pops back. Uberti has started shipping these, but I have not handled one yet and they are too new on the market to have been evaluated very well yet. At least I ain't seen any credible evaluations. As I understand it, the traditional design, with the firing pin fixed in hammer is still available.
There you have just about all I know about Ruger vs Uberti.
You pays your money, you takes your choice.