I'm partial to my Glock 17. But, I've been mulling the idea of chopping the grip to G19 length.
Reason? Not much different length. The part that mainly prints on a Glock, assuming a good IWB holster, is the back of the slide anyway, and a switch to a 19 won't change that any. As for slide length, in an IWB it makes no difference. Might as well keep the slightly better handling characteristics of the 17, I say.