My personal choice is Tetrix. We have used it for our 5 years that we have been a team. But since the rules have loosened up so that custom parts and other COTS are alowed. We HAVE moved away from the kit parts. Here is the 1st Part of the Manual for this next season. These are all of the rules except for the game and its rules. It is a good time to take a look at it.
I hope this helps.
http://www.usfirst.org/sites/default...ual_Part_I.pdf