I love the G19. I tried out a P99 at the gunshop the other day.
The P99 felt pretty comfortable, but then again, I've never ever picked up a non-ultracompact pistol that didn't feel comfortable. I thought it felt pretty good. Then I tried the trigger. I don't know if it was just the one I tried, but the double action was really unsmooth and "snappy". Felt like the trigger internals were made of cheap, flexible plastic. Single action was a little better, but had a long, strange take-up which let out an audible "click" in the middle of the stroke. I didn't like either trigger pull, but really didn't like the click, since someone might hear it if I ever needed to get a shot off silently (until the round goes off). Probably a rare event, but you never know.
No experience shooting a P99.
I was surprised. I have heard many individuals say how great the P99 trigger is. Oh well.
I think the G19 is great. High capactity, same trigger every time, reliable, and simply operation.