It is up to you what you want, I can only make suggestions. It is helpful to do research and it depneds on what kind of cash you are willing to dish out. I myself like the RB engines, my X12 never gave me any problems so I bought a V12 Rody for my other NTC3.
The key is cash flow!
#1 NTC3 RTR Modded w/JP Racing M12
#2 NTC3 Team Kit w/RB X12
#3 NTC3 FT Kit Ver.2 w/Rody RB V15 Turbo
Savage 4.6SS Kit