The two biggest differences I see between the two are that they use different material to make their grips and they are shaped very different. Hogue is using what I think is called "santoprene" and Pach is using rubber. They are the same in that apples and oranges are differnt but they are both fruit. Then the grip shapes are made to fit different hands and the feel in the hand.

If the wood Hogues aren't fitting and they leave a gap then they either aren't fitting correct or you have a K/L grip on a N or vice versa.

I kind of like the wood Hogues that don't have finger grooves, but I only have one set that I don't care for them on the gun they fit. Sounds like a good enough excuse to go buy another gun...