Hmm, my favorite characters would definitely be the P3 Protag, Makoto (even though I acknowledge him as Minato) and Junpei. Even though P4 was my first Persona game, I liked the Protag in 3 a bit more for some unknown reason that can't be explained. Most likely because I see so many people loving the 'Broswagonist' Yu Narukami, maybe I like being a hipster or something lol I don't know. As for Junpei, out of all the characters in P3 and P4, I felt Junpei had the best character development and growth out of everyone. Period. He went from jealous class-clown to being one of my most reliable bros and don't get me started on how much I loved him in P3P while playing as the female protagonist
...y u not let me date Junpei, Atlus?
As for least favorite characters, I'd go with Yukari and Rise. Yukari because, even though she may have had her reasons, she still acted like a mean [insert inappropriate word] when the game wasn't revolving around her. Even during the Answer, she acted as if she were to only who missed the Protag, even though, I'm sure Aigis may have missed him just as much, if not more. But, of course, while playing as the female protag in P3P, I liked her very, very much.
Now, as for Rise, I hate how she clings to the Protag even though it's obvious I decided to pair him with Ayane, his one true love and my OTP. Plus, she sucks as an analyzer. Fuuka may take a couple turns to give you information but at least she gives you something to work with; Rise essentially is Teddie with how at the beginning of the game he "remembers" the monsters' weaknesses for you. I saved you to be useful, Rise, why can't you do your one and only job correctly?
...And now I just realized I wrote a huge wall of text lol