I'd go with what ever is the best buy. I like RTRs because they are inexpensive and, like the one I bought, come with good parts. Even though I enjoy putting together cars and trucks, you should always disassemble your RTR and put it back together so you know its built to meet your standards. Also this gives you a chance to threadlock everything. In my opinion, its a win win situation. If you go with an RTR, it will be cheaper plus you can get to know your truck but the downside is a lot of RTR's out there have crappy parts. If you go with a kit, you can also know your truck more easily (only requires assembly but if you choose an RTR, you should disassemble and reassemble everything) and also be able to put any engine/radio you want. Bad side is they can cost a fortune especially if you want a good engine and radio.

With the 2 trucks you mentioned, I fine the Evader to be the cheapest and also have good parts. The RC10GT also has good parts but is a kit. They have the RC10GT Plus RTR but I find the Evader to be a better RTR. The Evader has a .18 engine which is not legal for racing so if you plan on doing a lot of racing, the RC10GT would be better.