I just went back to refresh my memory.
The Air Dream R lost 39 miles of range between the two tire/wheel combos (19s vs. 21s). On the 19's, there was 49 miles of range difference between the R and the P. On the 21's, there was only 30 miles of range difference between the R and the P. So a good bit of the range difference was due to tire/wheel sizes instead of powertrain output.
If Gravity maintains the choice between R and P and the range difference on the larger tires (which is what I would order) is only 30 miles as it was with the Air, I would probably stick with the Dream P. Remember that 30 miles of EPA range difference probably amounts to only around 23-25 miles of difference at sustained highway speeds. I doubt if that would make any difference when planning charging stops on a road trip, and you get the fun of the greater power on all the other driving you do, which is probably the vast majority of driving for most owners.