Well, as a character I actually find Adolin a bit annoying. Not that he's not a nice guy, but he just seems to get in the way a bit. (he's also a lot like Elend. Same as Elend annoyed me just a little bit as well ) But I think that he would be much happier with a sweeter, a bit less self-centred wife with less issues and who can concentrate more on making him happy than running around behind his back being a Radiant and lying to him. Don't get me wrong, I like Shallan a lot its just that I think that she isn't the best match for him and if they stayed together he would just get more and more insecure.
On the other hand, she seems to make Kaladin happier, is able to draw him out of his shell, and I feel like he has the potential to understand her and help her more than Adolin could. (if that makes any sense)