Interesting, I never tried the GT2 but there's a pro one up on sideline swap in FR, though the shipping and import cost to UK would make it more expensive than a SR 6.1.
I've got small hands (I'm 5'8 so I guess they are proportionally correct lol!) so liked being able to downsize the palm on the blocker. I guess I'd have to really crank the straps on a GT or 6.1 to get "locked in".
But for whatever reason the G3 felt like an extension of my body, the G4 sometimes feels like someone taped a back to front boxing glove to my hand...