I'm not sure - I mean, I'll try all new slots for a while.
To try to give examples, I've played Ching Ching on 3Dice quite a bit - I think the look of the slot is the best of all on 3Dice; on the other hand, the pay is worst also, IMO. So while I typically try to play each slot at least for one spin during each session, I put Ching at the bottom of my list, frequently skipping it entirely.
Slotronomicon (also 3Dice) is a game with gruesome icons/symbols, and not the best pays, but I just like it, and can't help but play it for any session I have. I think it has to do with the frequent bonus rounds, most of which pay very low (50x your bet is a very good bonus round, 200x is almost unheard of), but a rare bonus round can pay well, so there is the potential.