I don't know anything about a 7720, but I agree with Deereman that the major difference you will see is with the belt. I would set the cylinder speed you want and then look at the belt in both cases. Pick the one that has the variable speed sheaves in a more central position. In general, I would say it is better to be in the lower side of the gearbox whenever possible, but not if it has the variable sheaves maxed out which might allow the belt to slip. Just some thoughts.