That depends on a few of things:

1. culture 2. surveillance and consequence 3. maintenance.

some cultures are cleaner than others (Japan vs US, or India). if you record activities (remotely stored) and you can impose consequences plus you maintain the fleet properly (routinely and specially when people intentionally or accidentally soil interiors, that will go a long way.

I know I'd want vehicles which get routinely cleaned (BART vs JR subways and trains)