ORIGINAL: Access
I have found that the 2200KV on 4 cells is more than enough for just about any racing track. I wouldn't go with the 2650 over the 2200 unless space necessitated it.
To be completely honest, the 2200 is only 7mm longer, so space shouldnt be a huge issue, and they are the same price.............plus I chose the 2200 when i bought one.......................i would go with the 2200 too, they say running it on 4s is the "sweet spot". If you wanted the stupidity of 6s
, you could always go that way later! (Its fun)