If I had to choose one radio, I'd stay with Spektrum, the options of a programable Tx are too good to pass up. It was essential for me to learn to fly, without mixes and dual rates I would have given up long ago. In terms of tanks, like Dan said, servo recoil, etc are better controlled with a programable and setting up things like a raking MG are possible.

That said, it can be confusing. With all those options, one slip up somewhere with a travel adjustment, servo reverse or sub trim and it'll take a while to figure it out. Bill and I spent a good amount of time trying to figure out a miss in recoil on his StuG, only to find it a simple fix that we stumbled upon. Just last night I switched my Tammy Tiger I over to the DX6i so I could free up one of my old Futaba Attacks for the Panther. I set up the raking MG to the gear switch and wanted to be able to activate the main gun firing by the throttle cut button (right above the right stick). After a bunch of hair pulling, I got it to work, but the settings had to be so specific: elevator set to 106% (less and it wouldn't fire, over 108% and the gun would elevate with the stick) and subtrim to 36% up.

I have three Futabas and love them with a straight forward 4 channel Tamiya builds, but they're no go on stuff like the Kettenkrad where it demands some mixing.