The higher quality esc's handle more power, have different tuning/programming options, and are generally more robust. Look at the power ratings on the top spec esc's, you'll notice they are quite a bit higher.
Kv ratings do not directly equate to turns in any sensible way, but 6100 is pretty high/fast in terms of sensorless motors I think, so depending how big the tracks are you might consider using a slightly lower kv rating to give you more control, particularly indoors, where the tracks are typically smaller.
If your getting serious about racing then most people use sensored motors/esc's. This gives better control/feel at low revs as the esc knows where the rotor is at all times.
Sensorless will be fine for a bit of club racing though. I know many people use them and are very happy. It will be a good starting point if your new to it all. The higher spec, faster stuff can be much harder to drive until your used to it all.
If you going to a club or thinking about it, ask the other racers, people will be more than happy to advise you.
Hope it helps
