I only have my personal experience. Biking on the sidewalk lanes in Taipei creates a lot of scary close calls esp with children and dogs. On the road I only rarely have some issues with buses. Everyone is moving in the same direction so it's generally less scary.

I think in terms of deaths, the most dangerous issue is getting t-boned at an intersection by a car going fast through the intersection. I'm not sure how either setup really addresses that. You need to decrease overall traffic speed somehow. Chinese do this with speed cameras everywhere and electric scooters being much slower than gas powered ones (which are illegal most places now)