Right now 1/12 scale is coming up to a change... If you're going to be racing, check the tracks where you intend to race about what classes they are running, and what they are allowing. Most tracks are running 17.5 brushless in 1/12 scales, alongside 27 turn brushed motors as the stock class. Some tracks are allowing 13.5 brushless with a single cell 3.7 LiPO to run in this class as well, but it's not very common yet.
If you'll be racing at a track that allows the single cell LiPo, then I'd go that route. The only single cell LiPo for 1/12 cars at the moment is the SMC. If your local track isn't allowing that yet, get a few NIMH 4 cell packs.
For a 1/12 brushless speed control, the Tekin RS is pretty much the one to run. It's the smallest and lightest of the bunch. I have heard that the Tekin 17.5 motor is not that great in a 1/12 scale car, but I haven't actually tried one. I'm running Trinity Duo 17.5 and it's been great so far.