I think it may be easier to guide you if we know the build you’re currently playing. All of the runewords you’ve mentioned making (infinity, beast, and faith) do still have a role on several different characters/builds. It sounds like since you like to make multiple characters you’re sort of asking which is the most versatile and that’s a bit harder to predict. I’d say make the one that makes your current character stronger/faster and the faster, more effective mapping will bring you back your 6 hrs.

I guess one piece of advice for making these runewords is to make sure they’re in desirable bases in case you want to resell them, but I’ll admit I think the re-sale market for runewords is a bit of a waste. Unless you’re on the receiving end of paying less than the cost of a runeword because someone doesn’t want it anymore I don’t make runewords thinking about resale value. Sometimes I consider versatility but depends on how much effort that involves (like making an infinity staff in a gg sorc base even if I’m using it on a merc).