Don’t know that I have much to add that hasn’t already been covered. My progressive experience has been with Dillon. I load on a 550 that my Dad bought probably 30 years ago, a 650 with a case feeder I bought used 3-4 years ago, and occasionally on a SBD set up for 45ACP.
I load handgun cartridges on the Dillons, and rifle rounds on a couple single stage presses since I don’t load high volume for rifle. I mainly leave the 550 set up for LPP loading, and the 650 for higher volume 9mm and 45 ACP SPP brass loads, 38/357, and .40. I picked up the SBD a couple years ago as part of a package, and it works well too. Honestly, all 3 of them work good, and can benefit from a few tweaks and mods if one is so inclined.
For high volume loading sessions, the case feeder on the 650 or higher series is nice. The 550 is a very versatile machine, though. If I was doing high volume in only 2-3 handgun calibers, I’d look at the 650/750 series or up (1050/1100) with a case feeder. If doing quite a few calibers, the conversions and toolhead costs add up for the 1050 or 1100, and the initial cost is higher for the press. You can pick up used 550s sometimes for a good price.