This is a tough question, because on one hand, Mora is one of my favorite Daedric princes and I would rather not piss him off; on the other hand, Miraak could teach an entirely different (and, in my opinion, equally legitimate, due to the fact that he was the first Dragonborn) combatative side of the voice.
I think plots where you spend all your time undoing the villains work just to join them at the end are kind of goofy. If you could, at the end, convince Miraak to join you, then I'd be okay with that option. But after destroying his cult and all his little mind control shrines, etc. it doesn't make much sense to be like "You know what? I think you had the right of it after all."
Quick question, though: what is it people hope to learn from Miraak? He doesn't actually teach anything and I find it highly likely that anything he knows about being Dragonborn that you don't, he learned from Hermaeus Mora (the one who actually teaches you Dragonborn stuff, I might add). The only power I can remember Miraak exhibiting that no one teaches to the Dragonborn is consuming a dragon's soul directly for health.
No, even the offer of knowing dragonborn secrets from Miraak is tempting, I will not join him. One does not simply escape from Hermaeus Mora.
And Miraak has a soul of a dragon. Dragons have a innate will to dominate, My Dragonborn wants to dominate everything in this game. It all depends on your character.