.44s are like belly buttons, opinions, and...
Realistically nothing a .41 can do that a .44 couldn't, but I like going a bit against the grain. Bought my first .41 in spring of '08, and spoke up to claim my fourth tonight. All while the lone .44 in my collection has remained just that...the lone .44.
Honestly, the only benefit I can tell to the .41 is recoil. In my Marlin leverguns, identical except for caliber, max loads in the .41 recoil noticably lighter than max .44 loads. And that's just to my personal shoulder. YMMV.