I don't like the external balance plug but you can't beat SMC for quality and value. They will be my next lipo. 5200mah and 28C is perfect.
6000mah Maxamps is heavier too.
I have 6 lipos and only used 3 of them to run 3 classes with 3 qual. plus the main. 12 races on 3 lipos, but I have 2 chargers too.:0
I would say for racing 2 lipos per class would work.