Here at SI, we teach students to shoot in bursts of 4-6 rounds. A burst to the chest, and if that doesn't work, a burst to the face. Accordingly, I find it useful to look at a firearm's capacity in bursts, rather than the number of rounds.
5 or 6 shot revolver - 1 burst
1911, most single stack 9s - 2 bursts
Glock 26 - 2.5 bursts
Glock 19 - 3-4 bursts
Glock 17 - 4-5 bursts
Glock with Happy Stick - 7 bursts
So, if we think in terms of bursts, that 10+1 is 2 bursts, maybe 3 at most (and the last one is going to be a bit short). Given that 50.7% encounters involve 2 or more assailants, and 24% involve 3 or more, is that enough?
It's really your decision, but I'd prefer to carry something with a larger capacity if I possibly could.