RTR is a great way o ge into the hobby cheaply and easily.
If you are on a tight budget, then go RTR, as kit and electrics sperate will be another £100 ish on top.
If you are trying it out and not sure if its going to be long term, go RTR, if you are sure you are in it for the long haul and plan on racing regularly, go Kit/own electrics. As mentioned, they will be better and last longer and will be upgradeable and adjusable........
Happy Racing!!