Recently went to range with my DS Regal XL .22 caliber and did this exact same comparison, but my target was at 50 yards. I shot about 8 groups each of the two days. It was windy both days, but my results were much better with 18.1 vs 21 grain. Average group (7-8 shots per groups) size for the JSB 18’s was about 1” CTC, with about 5 of those shots hitting .5 to .75 inches in that group. I always seemed to manage 1 or 2 flyers in every group.
For the 21 Grain Baracuda I could not group as well. Groups were always greater than an inch; with most groups in the 2” range CTC. More flyers with the heavier pellets too. Borrowed a chrono and I was shooting about 750 FPS with the 21 grain and had considerably more pellet drop with the heavier pellets as you would expect. I’m reasonably confident I had the proper hold overs dialed in, but not enough velocity for 50 yards was my issue.
So, I know you wanted to see greater than 60 yards but in my case the 21’s would have shot much worse at 100 yards based on my 50 yard testing.
As an aside, many owners of the Regal .22 generally don’t shoot greater than 18 grains especially at longer distances. I think I’m starting to understand why.