the DR is bigger and heavier , the XB lighter and fraction smaller , most noticeable, length. dr will traverse a little rougher terrain easier.
come with same mill and drive train (except gear plate) which can and should be upgraded on XB.
Xb is quick and nimble. DR i think may have taller gears so fraction higher speed and obvious mass. TON more cool hop up parts for XB it seems .
the DR more true 1/5 scale, more durable (based on MT scale and parts) . for the weight of each really about the same , DR has way more chassis (like MT)
both are off gas steer out of the box , but dual servos can change that!