I used to be eaten up with the clay bird games and put hundreds of thousands of shells through P-W and MEC machines over 15-20 years. I'll try and condense my experience to help you choose but it will take a while to fully explain what the problems were.
I started with a single stage MEC Sizemaster. A nice machine that just won't keep up with league or tournament volumes. It is nice to have around for making relatively small lots of odd shells for a particular use. I use one to make loads for my wife's 20 ga.
P-W. The older machines were problematic because of timing problems. In the mid-90's they switched to a cam instead of the star-gear underneath the machine and that fixed the problem. These are really nice machines. I had two and loved them.....up to a point. They are almost indestructible. I sold one machine that had loaded maybe 75,000 shells and the buyer wouldn't believe I had used it that much because it had almost no wear marks anywhere on it. Still tight on all bushings, etc. I added the optional head to mine that would allow me to switch bushings without draining the reservoirs (this may be standard on current machines). And I bought an adapter that let me use MEC powder bushings instead of the more expensive and harder to find P-W or Hornady bushings.
But the P-W had two faults that drove me crazy and I sold both machines over this. The first is more of a nuisance. You place the wad into a little arm that then swings it into place under a ram that drives it into the hull. The shot drops through this same ram. The problem is that some wads out of every bag have fingers that are a little warped - they don't open fully and bloom out to let the ram and shot easily go down the center between them. In fact, some wads are warped and the fingers don't open up at all. When this kind of wad goes into the P-W, you get a mess. You get shot wads that are smashed down into the hull at funny angles, or shot that is not inside a shot cup at all, just laying on top of the smashed cup fingers, etc. It's not a safety issue but you sure aren't going to get a reliable pattern with those shells. You can minimize the issue by watching closely and trying to manually make sure the ram goes down between the fingers, but the machine doesn't give you any room to get your fingers in there and you can spend 10 minutes jacking with one wad and still not get it right. About the best you can do is set all the funky-looking wads off to one side until you have a big pile, put them in a pillow case, and throw them in a dryer for a few minutes. They tend to return to the shape the factory gave them when they get hot (but not always). It's not a magic cure but it helps. BTW, a Hornady 360 machine will give you this same problem for the same reason - the design of the swing arm that holds the wad.
The P-W problem that broke the camel's back for me had to do with crushed shells. Here's how it works: Each empty hull feeds up into a shell-holder from the bottom, and that shell-holder carries the hull around the cycle until the loaded shell is ejected. When each hull goes up into the holder, the brass base is resized by being squeezed into the lower ring of the shell-holder. When the loaded shell comes around to be ejected, it is shoved downward out of the shell-holder by a plunger. Occasionally, the downward force of the plunger would crush the upper part of the shell instead of punching the shell out of the holder. When this happens, the top of the shell smashes and balloons out and becomes too wide to fit down through the shell-holder (the shell stands maybe half an inch taller than the top of the stainless shell-holder). Now you are stuck and the machine is jammed.
The only ways to get that shell out is to cut the top of the shell off, which gets shot everywhere down into the guts of the machine (requiring a tear-down and clean out) or to use hand tools to try and drive the shell out. I would sometimes use a screwdriver to beat the top of the shell inward all around the circumference until I could drive it down into the shell-holder, but this took some time.
The problem was that the brass base of the hull was stuck into the holder so firmly that the plastic top of shell would crush before the brass would break free from the sizing ring. I thought maybe my holders were dirty, etc. I cleaned and reamed and polished those holders until they were like mirrors but could never fix the problem. At one point I even tried lubing the brass on each hull like with metallic reloading. Nothing worked. I found some after-market tools that were specifically made to help get crushed shells out of the holders without using a knife or my trusty screwdriver, so it couldn't have been just me that had these problems. Those tools made it easier to get out of a fix, but they still destroyed the shell and took several minutes to get the jam fixed.
I finally sold my last P-W around 2001. Maybe they've fixed the problem by now. Maybe with the internet (which was just getting going good by then) there were other cures that you might find today that weren't widely known back then. All I can tell is what happened to me (and all the other P-W users at my club). This problem was more common with AA hulls than it was with Federal Gold Medals, but the Federals were harder to clear because the plastic up top was thicker and tougher. I can't tell you how many times I had to tear that machine down to clear out a jam, and believe me, tearing the machine down with hulls in all the shell-holders is a royal pain and could take an hour or more when things got bad. And you can't get the partially-loaded hulls out of the holders, either. And it never happens until you have a tournament tomorrow and you need 4 more boxes of shells.
There were minor irritations with the P-Ws like spent primers all over the floor because they didn't pop out into the little cup or primers that got flipped out of position, etc., but you run into this kind of thing with any progressive reloader I've ever used, metallic or shotshell. It was the crushed hulls that killed the deal for me. The P-W is like a fancy sports car. When it's running good it's a dream, but when it goes bad you'll sure wish you'd bought that Ford.
When I was getting discouraged with the P-Ws I bought a MEC hydraulic progressive, the kind where you had to manually index the rotating table between strokes. I later swapped that loader out for the auto-indexing kind using the same hydraulic unit I had. This is the loader I still use today. It isn't as slick and impressive as the P-W but it has never jammed and never fails to operate. Even the issue with deformed wads is no problem at all. With the MEC, you don't have a fancy swing arm for the wads, you manually place the ram/feed tube down inside the wads as part of the standard procedure. Even the most warped, gnarly wad gives you no problem.
There are some things you have to watch with the MEC. Sometimes the transfer bar at the top that throws the powder charge and shot will stick if it gets dirty (the hydraulics push it one direction but it relies on a spring for the return stroke). If you're not paying attention and don't see that it stuck, you'll get a shell with no powder and the next shell will get no shot. If you are paying attention as it happens, it's no problem - just slap the transfer bar into place and all is good. If you don't catch it until you see the shell with no shot (hard to miss), you know not to crimp the shell in front of it and get a squib load. And the best thing is that whenever you have any problems, you simply pull out the shell that is out of whack. No jams, no machine tear-downs. No cussing and screaming.
The need to watch each stage of each step closely is pretty much the deal with any kind of progressive - you need to pay attention. I can kind of zone out when running a single stage, but a progressive requires your full attention unless you like surprises.
That's my experience over years of heavy use. I hope it helps you make a choice you're happy with.
