pros
1. stable when stationary
2. easier to steer
3. easier and faster to break
4. will go straight without constant fiddling
5. even more stable when climbing or descending hills, both head-on and snaking.
6. much safer, more reliable overall

cons
1. slightly more drag?
2. slightly more surface friction energy loss?
3. complexity and cost increased by 30~50% I guess.
4. takes up a bit less space when parked

I think tricycles are just better overall.

Was considering one of those balance bikes with THICK tires that are very stable with minimal effort, but I think the tires might

Also I think all bike tires should be full rubber ones that are impossible to puncture and needs very little maintenance. Those are just as comfortable.

There should be a law that bans all air filled bike tires, only allowing puncture-proof ones.