I like the Dillon 550 and have no experience with the Hornady. It's a standard around here for reloading pistol ammo in high volumes. It, like other progressive presses, requires occasional maintenance. Getting the maintenance kit at about $20 is a good idea because you'll have spares for all of the parts that are likely to need routine replacement. I particularly like having the "canned air" to blow the crud out of it after I'm done with each reloading session.
The most regular problem I encounter is in the primer feed. Take some extra time to learn that part of the mechanism so that you can make routine cleanings without it detracting too much from your reloading sessions. Mine needs some attention about once every 5,000 rounds.
I use mine only with one cartridge. If I were doing multiple cartridges I'd get extra tool heads so I didn't have to set up the dies every time I made a change. Also, I don't think I'd want to switch from cartridges requiring small primers and large primers. It's extra work in setup, although it only takes a few minutes to make the change.