For car/house, the 3" is pretty obviously the way to go, IMHO. For carry, the 3" will go darn near anywhere the 2.25" will, with the exception of pocket carry.
There are a lot less holster choices for the longer barrel, but a little looking around should still come up with something suitable.
I have the 3", and to this day, I still don't know if I wish I'd gotten the 2.25" (I think it's mostly that I still want a snubby for my collection). Like you, I got the sp101 for purposes other than carry (in my case, I bought the 3" for taking women to the range, and I thought sight radius & less muzzle flip were important). My thinking was that someday I'll buy a pre-lock 640 for carry purposes.
I love the way the sp101 points and handles, and after several thousand dry fires, I'm pretty happy with the trigger. Maybe some wolff springs or a trigger job someday.