This is hard for me to decide, as I'm not super deep into 4U at this point, but one thing I can say is that I personally prefered the farm in Tri. Someone else mentioned the cats working on the farm being comical, and I found that to be a charming area of the game and it is missed. The climbing and mounting is a game changer, but I can't help but wonder if perhaps its made the fights almost "too easy" if there is such a thing in MH. =p The in and out connectivity of 4's online aspect kicks the shit out of Tri.
If someone had not tried a MH game before and was on the fence, I'd recommend getting started with 4U as it feels to me to be a much smoother transition into the game than Tri felt. Perhaps it is because I now have prior MH experience now, but it just seemed much easier to get certain items to forge and upgrade gear right off the start. That said, I fully believe because of the timesink that is MH, that those hundreds and hundreds of hours are best spent in front of a 50" tv and not on a handheld screen. /shrug
edit and I didn't mind the water levels either. nice to have a different playstyle and environment here and there.
