The DD tail is definitely better. Good tail ESCs (from worst to best):
Castle Creations Pixie 7p - $30
Schultze (don't know the model #, but about $55 I think)
Trec - $55 (the best - specially made for electric heli tails with a computer interface)
No matter which ESC you get, disable the BEC by disconnecting the red (positive) RX connector lead. The main ESC's BEC will run the RX and servos.
I use a Pixie 7p and it's great, but some people swear by the more pricey ones. Do a search on them in this forum for more information.