Transitions are faster with a lighter pistol.
You mean transition from one target to the next? Oh, ok, that must be why ALL IPSC shooters shoot Glocks, right? I get it! Thanks.
I actually know at least one person who actually transitioned from one target to the next, 3 in total, with a “heavy” 1911, and all 3 of the bad guys hit the floor before they could get a shot out. I don't know how much faster you need to transition.
I carried a Taurus PT99AF for a few years, and although sometimes it felt a little heavy, I don't think it was that bad. I did try a Glock for weight, but decided my Taurus was better for me, more comfortable to carry although it was a bit heavier, and quicker for me to hit multiple targets with.
In the end, the weight of the gun is pretty much a personal preference, some like light plastic; others would never be caught with anything other than strong steel in their hands. My dad, who just turned 77, still carries his 1911 every single day. Try; just try to convince him that it would be more comfortable and better for him to carry Tupperware in his belt. I’ll wish you all the luck in the world and would ask not to be there, so I don’t have to laugh my butt off when he tells you off.
By the way, I know shoot mainly a 1911, and the only reason I didn't carry one when I carried the Taurus is just because I wasn't allowed to. I wish we had the right to carry here; I'd be lugging that heavy thing everywhere. YMMV, that’s why we have choices.