First off, I'd say the NanoQX is better to learn off of for a reason -- Acro flight mode. It's one of the VERY few micro quads that can be flown with the self level turned completely off, but still can switch back into the more stable modes at the press of a button. This single ability makes it better than most others because you can take your learning one step further in preparation for a larger quad.
That being said, it's useful, but not critical.
I've been very pleased with my Hubsan x4 in past -- very stable, can be very responsive, and durable. If you go this route, do at least get the lighted version -- it makes a difference.
I would avoid the Estes protoX/Hubsan Q4 (same thing) or the Cheerson X10 quads -- they're lots of fun, but twitchy fast, come with a cripplingly small transmitter and are so small they're hard to maintain orientation with. Neat toys, but horrid to learn off of. Do yourself a favor and pick something slightly bigger with a slightly better radio to learn on . . . then pick one up later, then those guys are fun to play with
