Mostly petty reasons. Sera's voice grates, I've been known to forget Varric exists, and Cole's creepy. More importantly, I like Dorian and Blackwall best. Not so sure I'll like Solas, but he seems interesting, and I want to make sure I get the banter.
I feel the same about Sera's voice. I don't think I could deal with listening to it for hours, dragging her around. lol
I liked Varric in DA2, but I'd sort of like to get to know the new people better, especially in the first run. Luckily, I actually like Cole. I think Dorian/Solas/Cole will get a lot of use from me, but Blackwall is another one I like quite a bit. Definitely my favorite warrior.