Do you mean you are considering buying a high capacity 45, or the possibility of facing a high cap 45 when you have 8 shots of .357?
If the possibility of being attacked by 5 people was greater than average, I would opt to have more than 8 rounds available. Glock 19/23/32
I typically carry a subcompact Glock that's 9 + 1
Yesterday, I carried my Glock 38 (45 GAP) 8 + 1
Strive to always carry the gun you would carry on the "bad" side of town.
My carry philosophy is "Something is worth doing is worth doing right" not "Something is better than nothing".