Things I would look for are what exactly are the things that your son loves about RC vehicles.
Does he gravitate more towards the speed of things, or does he really like the size of the 1/8 scale vehicles. Does he like the sound and smell of nitro or does he prefer the quite of electric?
I would say since you are wanting to stick with AE, I would probably pick him up either a T4 or the GT2 depending on what he likes, electric or nitro. I would then go to RPM's site and get everything I could that was made to beef up the vehicles since he will probably hit alot of stuff and be rough on them. A nice big bumper, and maybe even rig up the RPM GT2 Front arms.
Set it up so it has alittle push to it and he should be set. Also, dropping a nice mild brushless unit would be a nice touch since you get longer runtimes and really cut down on the maintenance, so he can just do more driving. Nitro different story of course.
If his heart is set on a 1/8 scale buggy, I would probably look at what bang for the buck you get and go from there. They are all pretty durable. I have the CEN Matrix, and it is extremely beefy and can be had cheap too.
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