You can delete your vote and choose again.
I know, but I'd have to revote for all of them. Blech. I'll just let it slide.
Anyway, I like Serana a lot, because she DOES comment on non-Dawnguard things. Not as much, but she'll comment on the weather, if you go somewhere extraordinary she'll say, if she likes you "Wow, this is beautiful. I'm glad you're here with me." it's pretty sweet.
But, she has crappy spells, and won't dual wield, which is lame. Then she unequips the sword I give her to throw off weak lightning spells and vampiric drain.. I wish there was a command to force a follower to equip something and change their fighting style, like Fallout. Tell them to use a bow, spell, weapon etc. J'zargo, for instance, has the lighting bolt spell. But he only uses it to defend himself when he's not a follower, so it's like wtf Bethesda. Even though J'zargo can go to level 81, it's more or less useless because he uses the same stuff at every level, the only bonus is more health.
However, my only and favorite follower is Sylgja. Yes, I ported my save to PC, and used console commands and whatnot to make her a follower. It works perfectly. She fights well, etc etc. Doesn't dual wield, but oh well. So now I get to have my gorgeous wife fighting beside me; oh, and Garmr. I increased both of their levels to 81 and made them essential so they weren't a burden to me.