I warmed up to Reshiram only initially, but now, I like both dragons equally. Reshiram is very elegant, while Zekrom is badass. They both have unique typings that I've been expecting long ago. Plus, I love how they embody the concept of Yin-Yang, so perhaps that makes me treat them as "one", and by the legends, it's canon that they were originally that "one".
Needless to say, I'm going for both. I ship them as well. :U