I've used a Dillon RL 550B alot over the years. Something that helped me stay consistent is to use lock rings with a set screw, like Hornady, Lyman or RCBS lock rings on the dies. They don't vibrate loose very easily, and go back in very consistently. As for reloading dies, use whatever you want. The Dillon powder measure that comes with the RL550B is very consistent with Winchester 231 or Bullseye, and the Accurate powders (#5,#7) work very well too. I use ONE powder measure, and just put it on top of the toolhead I am using at the time. It doesn't take long to turn the screw and setup the powder charge I need. I do three or four consecutive checks with my powder scale, and start zipping out rounds after that. By the way, 231 or Bullseye powder is extremely consistent.
Keeping one caliber on its own changeable toolhead is a good idea. You don't have to check the dies very often if you have the lock rings down snug. And PLEASE label what you have stuff setup for: use some painter's tape and a Sharpie marker so you can remember the caliber, powder charge, and bullet setup. Also make and keep a dummy reload round of what was on the machine(no powder or primer) so you can use it to check yourself if needed. That's a whole lot easier than breakin' out the dial calipers all the time. I make better rounds than I can buy on my machine. Git R Done!