And to add a third option into the mix, The Honey Badger doesn't use any mixing at all. I've got a transmitter that has has tank like controls on both sides (a bit like Panic Attack's original transmitter when you see it) though it does make going in a straight line a bit interesting if you don't push them both equally.

My transmitter is a Carson Reflex Stick 2 but they are jolly expensive - £95 on eBay. I'd go with Maxamuslead's or lowndsy's advice on this one if I was starting over again