I have the L48 R1, and when I used it (from the day it was released), it always preferred back spin. Maybe on say, CCC hole 18, heavy headwind, it might get more on that with top spin (downhill putt with nearly zero fairway roll to face plant into).
But 100% of the time, absolutely no exceptions, L48 R1 with fbs equals greater carry than any amount of top spin. I have demonstrated this to several other L48 R1 owners, and all have agreed after testing it.
The only reason I am using the L81 G20 driver now is because of the LACK of carry with the L48 R1. On STA hole 17 for instance, I had a 19mph headwind yesterday, and due to a flicker in the wind to the right, I barely made it to the fairway. With the L48 R1, I would have had to drive further left, leaving a 270+yd approach! Under non-(pure)headwind conditions, the L48 R1 can almost match the L81 G20. With a great tailwind, I am still only gaining about 5-10yds over the L48 R1, and that by sacrificing forgiveness. That L94 R11s driver is a long way off, and that L93 Black R1 will be long gone by the time I reach L93. So tempted to find another distraction for my evenings... (but, they already have the bulk of my cash, eh?)