If you want something more realistic, go with a Tamiya TLT to make a 1/10 scale out of the axles. It is realistic because it uses driveshafts and a center tranny (transfer case.) This is what my axles are from. Most of the money that goes into this hobby is for the electonics. When axles snap, the replacement parts are cheap. If you want a bigger driveshaft driven rig with monster tires, then go with a Tamiya TXT. They come with Rockwell style axles. There are others models out there, but they get hard to find. The Clodbuster is a non-driveshaft type of vehicle. It has one motor and gearbox on each axle and they work independently from each other. The plus on these are that all the weight is sitting on the axle and because there is no driveshafts, there is a lot more ground clearance at the belly. People have made some good crawlers out of an E-Maxx as well. Although they created a solid axle out of the independant suspention with super high ground clearance.
These guys do competitions and everything just like the real thing. And the slower your vehicle goes, the better.
For me, this was a good way to learn about suspension and how to 3 or 4 link an axle.
And one more thing, don't bother with Nitro engines. They will never perform as well as electric motors in the RC Crawling world. They are too high revving, clutches burn too quickly, and there is not enough torque to "crawl" over an obsticle.