SupaStox 1s/2s
 

My question is which kit would be better for circuit racing ???

My club allows 2s in the 1/12 class

I would definately go for the 1cell 13.5t option.
I ran a stock speed passion v3 21.5t motor on a blinky speedo with 2 cells at the Summer Shootout at CARS today and the speed difference was massive.