Getting the MBX4XR or the MBX-5 will not cost much of a difference. The X4 is harder to work on, it has extra stuff on the front and rear suspension that bends and binds easily. The shock shafts on the X5 are thicker and more durable (front shock shafts are the thing that breaks the easiest on any 8th scale.
8th scale buggies are by far the most durable RC cars. They are very fast, can jump like nothing else and have the highest fun factor of any RC cars out there. Whatever 8th scale buggy you get you will definaltely have fun with it.