I haven't used either of those specific transmitters, but I have previously owned a Futaba 7C and currently own a Futaba 14MZ. Both have been rock-solid performers. I have never lost a model because of them <<knock on wood>>.
That being said, I agree the Spectrum user interface is easier to understand and follow than Futaba's. It is just plain easier to program and setup your models. It’s so easy, I think I could do it without a manual. Futaba programming is not terribly hardier, just not as intuitive, IMHO. YMMV.
On the downside, there have been several issues with the Spectrum radios and receivers. To my knowledge, the DX6i has been the subject of two recalls. The first one was due to bad batch potentiometers (probably due to a parts vendor problem, not Spectrum) and the second was due to unexpected incompatibilities with their own receivers and a specific subset of DX6is. However, if you are buying new, it may not be a relevant issue.
horizonhobby.com/Products/Support.aspx?ProdID=SPMR6610
I would agree that being compatible with the Bind-n-Fly products is a big plus!!! I have considered buying one just for that reason alone.
In reality, it's kinda a 'coke vs pepsi' decision. I would recommend holding both in your hands and see which one feels better.
Good luck with your decision!
Tim