I've decided to disqualify the Sigma zoom. 800 gram is just too much when its other two competitors are 400 gram.
But now I just got into a new headache.
The Tamron 17-28 is an insane value proposition at 900 bucks.
It's the same, or slightly less weight as the 24GM.
The indecisiveness continues.
I guess this is just what happens when I have 3 extremely good lenses all vying for my wallet.
But I'm tipping towards the GM, because I don't have an F1,4 lens yet. And it would be nice to have one just in case of low-light emergency.