Get the 7C if you can afford it.
As a beginner you'll never know what you'd like to fly in the future and besides more mixing capabilities, the 7C can handle a helicopter.
The 6exa seem to be a great TX, and I've recomended it to a friend who's interested to start flying on a budget, but if it was me, I'd go for the 7C to get helicopter capabilities.
Changing TX later on will be more expensive than getting the 7C right away.

I have the 9C, the 7C has the same programming interface/buttons, it's very easy to learn and overview.