I got a 3" wico and a 3" (high-lip/golf) happs trackball.
My happs spins longer and the ball/casing fitting is better (no rattle) than my wico. My wico feels little smoother when I roll the ball, but the ball rattles a little if I hit it the right (wrong) way. I think others have found the wico smoother also. IMO, my happs has a slightly better lip around the ball than the wico; there's less space between the ball and the lip to catch my skin. Not that I even pinched my skin with either while
playing; I did pinch once while mousing around in windows.

I'm still debating which 3" I like more, though.
I bought two a happs mounting plates. I had to enlarge the wico mounting bolt holes a little so it would fit onto the plate, but it was very easy. Just re-drilled the holes with a slightly bigger drill bit.
Oh, and the happs trackball fits the mounting "perfectly", while the wico lip diameter is a little smaller, so there's a small gap between the plate and the trackball lip. (Not that I can see it; with the black TB casing & black mounting plate.) If you cover it with graphics, no worries at all.
As for lexan, the happs high-
lip (I didn't know about the high-ball) and the benson have spacers that can be removed so the lip of the ball sits higher than the happs mounting plate. The wico I got and the older happs 3" don't have the spacers, so they can only be at the level of the mounting plate.
Casings:
The happs trackball casing is the smallest, the wico a little bigger, and the benson the largest of these three. So a bigger hole would need to be cut for the benson than the wico, a little smaller hole for the happs than the wico.
Hope not repeating stuff you already know.