Well, I am the P99 guy here on this site - a huge fan. I have prev had a Glock 17, 19, 26 and 34. I only have the 34 now (it has a stock lighter trigger, and a few other features I like, compared to the standard Glock models). I carried the Glock 26 for 8 years until I discovered the P99 last year. I finally ditched it and got my compact P99 last Nov. Love the gun. Much better trigger too. The SA trigger on the P99c A/S is a dream.
Other than the G34, I really don't like the Glock trigger. And, even the G34 trigger is kinda mushy (its just lighter than the other Glocks). I think the P99 or P99c is more ergonomic too.
SInce U have shot both, you took the biggest step. Several others here are interested in the P99, but have never tried one before. If you have shot it and like it - get the P99.
One feature that is nice compared to other brands is that the Walther has user adj sights. You can swop out the front sight to any of 4 supplied front sights. And, U can adj the rear sight w/ a small screw driver for windage. U can also remove the sights yourself and put on your own night sights if U wish. So, no gunsmiths, sight pusher devices, etc.