good brushless setup advice

[secondwaiting]

so hows this...

mamba max esc
Feigao brushless motor 540 8xl
RC-Monster Brushless Heatsink/clamp
Ultimate BEC
and two Lipo 8000HV 2S2P 7.4V Packs




or would this be better....

Quark Monster Pro 125B Brushless Sensorless Speed Controller
Feigao brushless motor 540 8L
heatsink
ultimate BEC
and two Lipo 8000HV 2s2p7.4V Packs



and how much run time would i lose if i got two Lipo 4200HV 2S2P 7.4V Packs instead? can i even use those?


by the way, this is my first brushless system im putting together, so is the wiring and connecting and everything going to be difficult for me?
thanks again for all your help