How did this become an "either/or" debate? The first few posters had some interesting remarks on rethinking the traditional roles of BUG and main carry, with the thinking being the smaller gun might be easier to access RIGHT NOW under pressure depending on mode of carry. Capacity debates are so boring.
And yes, a Glock 19 is far easier to defend/deflect than a snubby. I've done it with blue guns in Krav Maga and a G19-size gives you plenty of barrel and frame to work with (relax--I'm not saying it's easy to do or your 19 is going to get stripped, I'm just saying it's easier than with the snub). The snub requires attacking the hand holding it and the shooter can power right through your grasp.