The RTR does not have any CNC susp holders, so it would be cheaper in the long run to get the FRE from the start if you plane on racing it. Also, the servos are slow, so that would be a must upgrade for racing also.
The truck is the easiest 1/8 Truck to drive. It has tons of steering and traction and does not get out of shape (a quote from a Kyosho ST-R driver who drove a Matrix TR Arena last weekend). The TR Arena has more down travel then any other truggy that I know of so it handle the bumps and jumps the best imo.