The lighter setup will serve you much better. A great motor with a 12 cell single series pack will only weigh 2.1 kg and give much more power and much better power to weight and 12-20 minute runtime depending on gearing.

The Neu 1917 variant I sell has 8mm shaft and fan and runs approx 18500 on 10 cells (5.2hp peak) or 23000 on 12 (8.5hp peak) - they weigh approx 1.1lbs. They run cool with bucket loads of power and cost $249. I recommend a sock or a open cell foam filter for motor cooling.

You can use cheap esc like the turnigy 200 and moderate rate cells - at least 30C cont and have a fast relaible car.