The 6.5x20 is a great scope.
I have two of them.
Neither is mounted on a spring airgun, though they have been.
Whereas I have the following, from memory, on springers:
2-7x28
1.5-6x32
4x28
4x32 (twice)
6x32
6x42
3-9x40
3.5-10x40
4-12x40
The 6.5-20x40 is too long, and just too much scope.
I am prejudiced. I grew up when 4x40 was a big scope for airguns, and 4-12x40 or 3-9x50 top of the range.
But they are all you need at springer ranges. Rabbit sniping from a bipod-fitted PCP maybe higher mag is useful, but not on a general use Pro Sport.
At a practical level, Leupolds have long eye relief and the 6.5-20s are long scopes, so they will cover your loading port, which is, at best, annoying.