Truggies are super tough, I don't think you'll find a monster truck quite as tough, but a monster truck is still very tough also. As far as motors go, you can go with a high performance engine, a nova rossi, a OS V spec .30, A GRP engine or a picco .28, I have heard they are extremely powerful. I will say my truggy can be brutally beaten, and holds up well until you challange a brick wall, in most cases it does not matter what you are driving, you'll lose in that battle. How about a Losi Muggy, a cross between a monster and a truggy?

Truggies have lower ground clearance but will still go most anywhere, the monster trucks have higher ground clearance, and will go in rougher places but will flip easier than a truggy. Its a real toss up. I have both and love both. The truggy is just a brutal beast, begging to be beat on. (saying break me if you can). Both are great.

The one thing I will add to all this is be prepared to be challanged by the nitro tuning aspect, its not that tricky, but can be challanging. Your truck may run great one day and need a totally different tune another day. Break in is challanging. Carry spare glow plugs, start with manufacture needle settings, Only tune the high speed needle first through break in, and then tune your low speed needle, follow the instructions, and only make very small 1/8 or 1/12 adjustments, less is more (trust me) I used to tune to much and would get my carb all out of wack.

There is a great guy on youtube called squirrel who goes into all aspects of tuning and different methods of break in, excellent stuff. I follow his break in method. You'll learn a tremedous amount from his tuning videos, probably 12 or more, and its free stuff. Oh try checking out truggies in action on youtube or lst xxl. The videos will give you an idea which is tougher. Just type the names you find plenty of videos.

good luck