12th is cheaper and waaaayyy more fun. For two reasons, IMHO...
The class is stable. You will not need to buy the latest thing every week/month/season, and there is a limited choice of things that work (tyres, motors, cells, etc.) This is down to the rules, and the fact that the cars are very light compared to TC.
It's down to the driver. No other class rewards a good driver more than 12th. In our BRCA National Series this year, one of our best drivers has made the A Final in Mod with a 17T and a 15T brushed motor and 'shop' cells. That's against matched cells and brushless motors.
12th is RC Electrics' best kept secret!!