I found the XXX-4 a great car to run. I am a failry inexperienced driver, so I don't have the intrciate knowledge of some of the other drivers here, but it was a good car. I found it no worse in the bumpy bits than my B4 (I know, 2wd vs 4wd), but I had a fairly "unorthodox" setup for rough terain
I just sold it to get a B44, mainly because I have the B4 and they share some parts, I also wanted to try something new.
In the end, i'd say go with whatever car has the best parts support. Unless you are a very competent driver, the small performance differences in the top cars won't affect you much, it's more about getting them set-up right