some important specs:

-250 vs. 10 model memory

-Voice alerts ("Gear Up", "Landing Flaps!", etc.."

-Back lit screen

-higher resolution screen

-Wireless Buddy box

Afterthought, get the battery too :)

dx7 and 9 come with a battery, but the dx6 + a battery is about $50 cheaper than a dx7.

From my experience, I bought the dx6i, then almost immidiately had to upgrade to a Tx that held more models, then had to upgrade again for channels, then again.... Long story short, If you're getting into this hobby, get the best radio you can afford with as many features as you think you'll ever need, then double it :D I'm 3 years in and now have the $500 dx9... I hope that will finally last me more than a year as the others haven't!!