I bought a 650 just because, but use my 550 a lot. I have something like 10 conversions for it, & it's very simple to swap out & run 400-500rds then swap something else. I love the 650 for pure production. Stay with the same primer size & swaps are simple too. It's nice to pop into the garage & dot off 200rds for a sat match in 20min from start to finish, including loading primer tubes & checking initial powder charge.