I only have the 300B amp so I can only describe that sound, and I should compare it to other 300B amps, which I don't have.
I have 3 OTLs of which the Crack but I don't have the Glenn OTL. The only one who comes close to having your amp selection is Clayton, but as far as I know he's more of an "enjoyer" then a talker, but maybe if you ask him nicely he'll help you out.
Feel free to buy me a Glenn OTL and I'll give you a 2000 word review/comparison with my other OTL gear
I'd just pm one of the guys with an OTL here to ask if they can describe the sound of their unit. DMinches just gave you a short impression already. Good luck!