the answer to this question all depends on you and your experience/budget. as mentioned above, the SS kit is just that, a kit. it requires to to actually build all the major sections of the truck. if you have some experience in hopping up RC trucks then get the kit. it will however require you to buy certain items if you dont already have them (CA glue, tools, exacto knife, etc). next comes the budget part. since this is a kit, you'll need to provide your own radio sytem (transmitter, servo and reciever). depending on what you buy this will set you back 100-400+ bucks on top of the cost of the kit.
so to answer your question, if you are brand new to hobby with little experience or support tools, get the RTR version. if you have money for the radio gear and experience/drive to build your on truck, get the SS kit.