Having shot and owned both for many years, IMHO, the .357 will provide a "sharper" felt recoil with hot loads and the .44 will give you more of a 'push' in the recoil...It's hard to explain until you've been there...
That being said, both are powerhouses in their own right, both can be shot with lighter and more shooter friendly loads, and while the difference in size of a 4" S&W K or L frame or a 4" S&W N frame is negligible, it really boils down to to what feels best in your hand and the intended purpose.
The 2.5" versions are easier to carry from a space limitation, but you will find that accuracy suffers, unless you practice a lot with different positions and targets....
While not in your original post, you might want to look at the one by Taurus called "The Judge"... It shoots either .45 Long Colts, or .410 shells... both are devastating rounds as well...especially if you reload and swage your lead wafers for the .410... /ubbthreads/images/graemlins/grinning-smiley-003.gif