I have been reloading 38 Special on an RL1050B since 1988 and 38 Super on a Super 1050 since 2006. I also have a couple of XL650’s for 9mm and rifle.
The quick answer to your question….the Super1050 has a longer stroke length for rifle cartridge reloading and has a different bottom crank assembly.
I have not heard of a 1050XL. They are all great presses and will not disappoint.