I'll give you that buses tend to be more predictable - they run fixed routes, you can guess where the stops are - but my biggest problem is whether they can see me or not. They are large so if they don't see me and start moving while I'm trying to pass it could end badly. Usually I try to only pass if they just stopped and I clearly have plenty of room and time.

Cars tend to scare me more as there are way too many impatient drivers who are all to happy to speed around me without much clearance and then cut me off. And they could easily misinterpret me weaving a little to avoid a bump as me scooting over it pulling over for them or starting a turn. And don't get me started on how many cars have tried to right turn on red arrows across bike lanes which have a green signal.

Other bicyclists and pedestrians often suck too, but worst case if I run into them is pain, not death.