I LIKE my Bar Mitts for cold rides. Not for cool rides.
Size L on my drop-bar bike. They are still a bit constrictive. I spend most of my time riding on the hoods anyhow.
I love having all the dexterity to needed work the brifters.
It takes about 30 seconds to put them on or take them off.
If the day warms up and you remove the mitts, they take up less room in panniers than bulky ski mitt types of gloves. They flatten nicely.