OK. I'm going to start by assuming you're looking at a post-1973 gun, aka "New Model", "Two Screw" or "came with a transfer bar from the get-go". Prior to '73 things get more complex
.
Most Ruger Blackhawks and all "Original Vaqueros" were built on a large frame capable of coping with the 44Mag. When chambered in 45LC these things really re-write the book on what that caliber can do - 45LC+P ammo runs as hot as 325gr @ 1,300fps, which is hotter than most 44Mag fodder. When chambered in 357Mag you can push them to pretty crazy velocities if handloading.
All the Ruger SAs are done to the same heat-treat standards. You can take a 357 Blackhawk, swap to a 44 barrel, ream the original cylinder to 44Mag and presto, instant (and perfectly safe) 44Mag. This is NOT something most other brands support.
The Bisley models had adjustable sights like a Blackhawk but the funky hammer/trigger/grips...which are noted as being better for dealing with big recoil.
The "Old Vaquero" was built in 44Mag, and in 45LC could take the crazy +P stuff.
There were also "Bisley Vaqueros".
The "Old Vaquero" large-frame product line is now extinct. It's been replaced by the "New Vaquero", which is smaller and weaker yet has significant improvements in average quality and handling. The New Vaquero is often called a "mid frame" and is similar in size and heft to the Colt SAA or it's various Italian clones...which is likely what ol' pot-puffer was packin' on TV.
The New Vaq isn't being made in 44Mag as it's not strong enough. In 45LC it can't take the wildest loads - it tops out around a 260gr hardcast at 1,000fps, or a 225gr jacketed at 950ish. You'll also see some 200gr JHPs doing up to 1,100ish and Speer makes a nice 250gr JHP doing about 875-925 range. Those are the most fun a New Vaq can stand. In 357Mag you can load any factory round but you can't handload much past that.
Despite being a Colt "near clone" it has a transfer bar safety and coil springs. It's also compatible with many parts from it's larger cousins...you can swap grip frames, hammers, triggers and a few other bits.
There's one other Ruger mid-frame size single action: the 50th Anniversary 357Magnum Blackhawk Flattop, the only adjustable-sight mid-frame gun made so far. It's basically equivelent to a Colt New Frontier (adjustable sight) instead of SAA (fixed sight like the Vaquero). Another damned fine gun, moderately low production numbers but they're available and not rare enough to make a safe queen out of. It's the only post-73 "Blackhawk" that can't be upgraded to 44Mag.
Holmux just showed you a pic of a "Hunter model" large-frame. These are real slick if you like "big". They have a 7.5" long heavier barrel with integrated scope ring mounts. Most are 44Mag, some have been done in 41Mag and others in 45LC. They also come in Bisley and standard flavor hammer/trigger/grip sets...I recommend Bisley for big power.
If you're NOT looking for big power, consider the New Vaq or the 50th 357. Large-frame Rugers had cylinders that were drilled all six bores at once with a special machine with six drill bits, which were sometimes "off" enough to get variances between bores. The mid-frame cylinders are made one bore at a time with the same bit in sequence and are coming out with zero variance. Average accuracy and fit'n'finish is higher. My 357 New Vaq is an excellent shooter. Those looking for peak accuracy in the large frames often deliberately buy one in a smaller bore (say, 357) and have it reamed up to 44Mag or 45LC and re-barreled, making for a tighter gun than most factory specimens.
There are three different transfer-bar-equipped (completely drop-safe) Colt SAA near-clones: the Taurus Gaucho, Beretta Stampede and Ruger New Vaq. Pretty much NOBODY is complaining about Ruger mid-frame quality issues. Complaints about the Gaucho are numerous on this and other forums, with the Beretta doing better than Taurus but still not to Ruger reliability levels and certainly not able to match Ruger's post-sale support.
What else...the worst thing about the New Vaq is it's cheesy fake color case in the non-stainless models. There's a special distributor run available of all-blue New Vaqs with wonderful white smooth micarta grips, worth tracking down if you're interested. I can find out which distributor run that is. They're also about to do a run of 500 3.5" barreled mutants with SuperBlackHawk swoopy hammers, which is a mod I've already done to mine and is really cool.
Mine:
http://thehighroad.org/showthread.php?t=269453
The new special-run shorty:
http://thehighroad.org/showthread.php?t=269469
