I used to have two 1050's. One set up with LP system and one with SP's. I only loaded .45 ACP on the LP 1050 and realized that was stupid. Just buy SP .45ACP brass...duh!!!!
I do not shoot enough LP rifle to justify using a progressive, but if I did, the 550 would be more than adequate. $500 for the press, quick and cheap caliber changes, and a life time warranty....not seeing the need for anything better.
I have stopped shooting much .45 so use the 1050 for 9mm, .38 and .40. A bit of a PITA to do a caliber change but not that bad. Cheaper for me to load 2000 at a time as brass for those calibers is a cheap and I can crank out 2000 rounds in 3 hours or so. I leave it set up in .38 as that is what I shoot the most. If I need 500-600 on short notice it takes an hour.
I owned a 650 and much prefer the 1050. Priming on the downstroke is a major advantage as no "feel" is required. But I never saw it not being built well enough to need beefing up....but then I only loaded pistol on it.
If I was 20 years younger and still shooting competitively, I would get the Mark 7.