The x01 is strictly for the street. Do you have the space to open it up? Then what? Others to race against? I test new gear combos and break in new nitro motors on the street. Gets boring fast.
The xmaxx is big. Do you have the space for it? Plus the batteries are costly, if you want to have some real fun. Kind of why we've held off for now. The full sized Summit is a lot more affordable, if you're looking for big, and based off the Revo.
My vote is still for the Revo. You could easily turn it into a Summit, or put street tires on it and break 100 mph. Tons of videos on Youtube.
That's why I keep the old HPI Nitro RS4 MT Racer around. (O.S. .18 CV-R with a Cvec pipe) Put on the original body, street tires and a certain set of gears...it's a blast on the street. Put on a truck body, off road tires and change the gears...it's a blast in the dirt. Look for those crossover vehicles. Twice the fun for much less.