belt and quality IGH is ideal for the absolute ultimate reliability and least maintenance in dirty, bouncy, rough riding. a good friend rode his purpose built bike with rohloff and gates belt more or less from California to the end of South America, and back, with no drivetrain maintenance other than replacing the belt once. this is on road, off road, in the most extreme conditions and terrain, an order of magnitude harder than anything I’d ride… but if I did it, I wouldn’t do it with an exposed chain, cogs, and fragile derailleur.
at the other extreme, IGH and belt are fantastic for city riding, no grease, no adjustments, shifting while stopped, etc.
but they’re very heavy, expensive, less customizable, many can’t be shifted under load, perhaps have a bit more drag depending on who you ask….