Ask me, and I'll say the fewer buttons, sticks and readouts your drivers have to deal with to control the 'bot, the better. Complexity kills. Give the drivers the ability to fully control the 'bot, but as simply as possible.
One stick always felt much better for me. I also noticed that two stick drivers had the tendency to really slam the sticks back and forth, because accelerating evenly was such a hassle. It's easier to just throw both sticks to the stops. One stickers had an easier time of accelerating smoothly, and I'm sure that this translates into longer lives for gearboxes.
Above all else, it is a matter of choice for the driver. It's just that one stick is the right one
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-Andy A.