Oh man, anon, this is a tricky question because I love them both equally, but in different ways!
I will say that, going into season 3, I’m a little more excited about Swan Queen. I’ve been a little frustrated with how Rumbelle has been written after “The Outsider” — or, really, after “The Crocodile” — lots of silly external obstacles for Rumpel and Belle, not enough dealing with the actual problems they have, separated for fairly bullshit reasons in the finale, etc. etc., whereas I’m really liking the developments for Regina/Emma that have happened in the last few episodes of s2 and I’m REALLY excited about the possibilities for SwanQueen in s3. Two people forced into close quarters, who kind of love each other and also kind of dislike each other, but who are forced to work together is basically MY FAVORITE TROPE OF ALL TIME (haha as illustrated by every fic I’ve ever written), so. I’m pret-ty excited about that storyline. Whereas with Rumbelle, my favorite thing is their kind of day-to-day interactions and that…is not looking promising for s3 sadly.
In closing: I can’t really decide because they are both awesome, but I will say that I’m definitely more excited about SwanQueen’s storyline in s3.