Re:
The sti type clean up the bar area as only one clamp, handy if you want to fit dropper or fork/shock lockout levers.
I think the only real downside is if/when you want to change brakes or shifters, as you have to change both.
There was a period when the Shimano ones looked ugly as anything, around the 2000s I think (xtr m960 etc), but aside from that they look fine, work as good as separates. I've got some NOS xtr m970 ones I plan to use, and have a few xtr m952 on builds, and some xt m739s in a box somewhere.