No question, .44 Mag.
It has been my experience that no handgun round is "plenty" for humans. A 180 grain bullet at 1700 fps, is nothing to sneeze at however.
If I have to reload in a defensive situation, I am in trouble. If I am in trouble, I have speedloaders for my 4" Model 29.
I don't own a 10mm, but my Model 29 is supremly accurate, the action is unbelieveable, and it isn't all that huge to carry.
You don't mention how far past 25 yards we are talking about but I can hit a paper plate offhand at 50 yards more often than not with my .44 (granted, no one is shooting back and I am taking all the time in the world to do it).
If we are talking about defense against large animals, then the heavyweight .44 bullets come into play. And, they have taken every animal on the face of the earth out of a handgun.
All that being said, I would still prefer a .357 also. Why, I can't justify it, but I would.