Hey Daf,
Its been a while, nice to see you online
I have been racing my MBX5T with a NEU 1515 2Y for some time and I really don't notice much, if any, "drag brake" when jumping. I also run a 6 Pole Mega motor and I don't notice much, if any, "drag brake" on that truck either.
As for Brake setups, personally I would rather use motor braking on all my vehicles but I've found that cars with center diff's perform much better for me with brake bias (mostly rear only). Also, the Tekno guys use the 2 speed Revo trans which requires mech brakes due to the oneway bearing so the advantages they list aren't option's but requirements.
I like Mikes Hybrid brake suggestion using a very small, light weight servo for rear brakes only and motor brakes for the remainng percentage of braking power you desire.