The sizemaster is good in any gauge you like. The 410 is a little harder to load for because it's so small but you save a lot of money. i load for them all. You'll probably end up getting more after you start.
IMHO I'd stick with mec 600 JR unless you plan on shooting thousands of rounds. The cost and complexity is unnecessary for progressive reloaders for only reloading hundreds of rounds a year.
