Well there are several things about your question that are not clear;
What size models do you intend to fly being the biggest one. If you have no intention of ever getting above .40 to .60 size sport models then there is probably no reason to worry about the dual elevator servos or any of the other additional features the 9 offers.
If you're set on the 7 due to the price difference, why ask the question and then argue with those who would offer advice? It makes absolutely no difference to me what radio you buy. You asked for a feature that would definitely make a difference in the two radios and I gave you one that is, in my mind, the number one reason although there are others.
Buy what you want...
