A scaler = alot less performance but looks like a real pickup or like the wraith, a rock buggy.
A crawler, wont look nearly as real but will out perform a scaler almost always.
If your just doing back yard stuff on smaller rocks/dirt, then a scaler might be for you. Like what HPI-killer has.
If you dont think you will compete at crawling, then a scaler might be more fun since you can always do little "scale" things to it for fun to make it look more realistic and scale or a 1:1.
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You could always do a Losi Mini crawler too, their fun, need lots of upgrade if you use them much and are of course, small, which makes the terrian they will beable to use alot smaller but they are cheap RTR.
Rpp has them for $209 once in your cart...
http://www.rpphobby.com/product_p/losb0222.htm