I have limited experience only between my New Holland TC33D and my Massey 1736. My preference is my New Holland with its rocker pedal.
First, you can not simultaneously go forward and backwards as there is only one pedal. Not that I have tried or accidently hit both pedals on my Massey but it seems like it could be done (if you did it, I wonder which direction you would go?)
Second, it is intuitive, to go forward you apply pressure with your toes. To go backwards you apply pressure with your heal. On my Massey the 2 pedals are side by side and until you learn which one is forward and which one is reverse mistakes can happen.
Third, and while I am guessing this not as much a pedal issue, but more in the design of the hydrostatic system. On my New Holland I can be on a hill facing down and take my foot off the brake and creep backwards at the slowest of speeds without ever moving forward. With my Massey, as soon as you remove your foot from the brake the tractor begins to roll forward down the hill. I've tried pushing down on the reverse pedal before I let my foot off the brake but there must be an interlock which does not allow the transmission to engage if the brake is on. While the delay is only a second or 2, you can roll forward almost half a foot before the reverse kicks in, which is not a comfortable feeling.