Astarion, because (1) he makes me laugh, and (2) he literally has more content than the other companions (except maybe Shadowheart?) so he feels more "alive." That being said, the other companions should have had an equal amount of content (thinking of poor Karlach and Wyll especially).
In terms of who I'd actually get along with IRL, Wyll definitely wins. That being said I like Lae'zel, Gale, and Minthara a lot. Shadowheart and I agree on basically everything but I don't find her that interesting (and they trashed
to prop SH up so I'm bitter).
