We ran 40s on our Xflow for years. They were brand new with the right progression holes for the engine, set up by a man who knew his Weber onions. Much as you say, started hot or cold, seemed to run fine. Any 'character*' was put down to it having a moderate state of tune and the folklore of 'it's a lumpy cam, it'll always be a bit rubbish below 3000rpm'. Fitted mapped ignition to help with the cranking (11:1 CR and 13 degrees of static advance can be demanding on a small bettery) and discovered it was a different car - having fitted the ECU, converting to FI was a simple step and a set of GSXR 600 TBs finished the job. It probably didn't make any more power on FI, but it was just so much better to drive and more economical too. The 'character*' just vanished.
I think it's a case of carbs, even properly set up (increasingly hard to do these days) are always going to have more compromises than EFI. Badly set up EFI is no joke either - seen some epic fails there too.
* 'character' defined as spitting, farting, popping, dribbling petrol everywhere, flooding if you didn't get the starting technique just right, pants mpg even if driven like a saint, perpetual odor of petrol.