Happy Holidays!
One disadvantage I see on an integrated handlebar is if you put it into a bike box for travel.It is easier to unmount/mount the bar from the stem than the whole stem/bar.I should forget it, but I'm still traumatized after seeing a crack in my first carbon stem.So all my stems are stupidly alloy now...
I've been running on carbon integrated handlebars for MTB for about 5 years and have been very happy. never had a problem in the bars despite breaking 3 frames.