I much prefer the feel of the 19 over the 17 (Tokyo Marui G19 can't come soon enough!), But I have small hands, so this is the reason why. Having said that, the 17 doesn't feel too large.
The 19 feels more planted in my hands, more pointable.
The smaller mags are a problem, but it'll take the 17 mags and the 50 round long mags.