RE: 25 or 4.6?
SS 4.6 all the way. Get the 25RTR if your afraid to build the kit. HPI's directions are the best in the industry, so if you have a 3rd grade education or better it should be easy. If your new to building kits take your time, so what if it takes you a day or two to get it running. And if you get the RTR you'll be taking apart eventually any way.