45 SMLs give you the largest variety of projectile and powder choices of any ML i can imagine. You can shoot big lead conicals with subs/Real black. You can shoot sabotless 45s upto 2500fps with ease and even BH209 makes excellent fps used this way. Plus of course 45x40 sabots past 2800 fps and it will handle the heavier 40s like the PR QTs or DCs even better than slower twist sub guns.

50cal SMLs can do many of the same things very well except shooting 50x40s usually and sabotless is a bigger PITA since the sizing dies are pretty much custom order only. My NULA though is a nice light gun that shoots sabots/bullets in the 225-275gr range fantastic upto 2300fps and never needs more than 43gr of powder. It was the one that sparked my interest just because its so light and recoil is surprisingly mild. The Savage 50 barely got my attention compared to the GMB54 for hunting.