I like all party members in the persona series, but as for my favorite, I'd say Yusuke Kitagawa. I find him very charming and mature, which is kinda rare in persona boys excluding Akechi wait, he's a psychopath, since a lot of them are the stereotypical reckless or "never studies" character (i still like those guys though). I also relate to him in many ways, we're both artists, and overall, he's very well written.