Things will be far from a happy ending for everyone–there is still the threat of Captain Hook and Cora coming up, as well as other characters that may prove as a potential risk.
Neither Emma and Regina are a hundred percent stable–each of them have isues and hardships that they need help with. But, on the whole, I think Emma is a bit better. Regina has hurt Henry before–he said so himself that she made him think he was crazy. She revealed to the whole town that he was born in jail, she had Archie purposely hurt Henry to make him feel horrible, and she has used Henry to get what she wants–Skin Deep with Mr. Gold in jail is an example.
Emma may have her problems, but she never would have put Henry in that position if she could help it, nor would she ever hurt him emotionally. Regina may have given Henry all that a boy his age could ever want, but emotionally, she has hurt him numerous times.
I think for Regina, the moment where she wanted to change not only came from We Are Both, but from A Land Without Magic. That was the moment she had thought he was truly dead and never coming back, that he had almost died all because she let her wraith get in the way. That moment when she saw him, seemingly dead, was sort of an epiphany for her–especially when Emma’s kiss was the one to wake Henry up.