Personally, I like Plucky. I have her Amiibo and moved her in because I wanted Del OUT. I didn't care much for Plucky at first, but she grew on me. I liked how her little feathered butt would wiggle when she happily greeted me- it was so cute! Plus, I'm a sucker for the sisterly personality. It's my top favorite, even though everyone else seems to hate it, lol. AND she has the play hobby- watching her run around, pretending to fly, is TOO. CUTE
I also like Ava, because she has a nice, simple design. She's just a simple chicken. Living a perfectly normal life. Like, if you said, "Hey, I have an anthropomorphic chicken in my town." she seems like how you'd expect her to look, and how you'd expect her to act.
For least favorite, I know it's an unpopular opinion, but Ken. He's just too... intense for me. I like villagers whose designs are neutral OR match their species. And he's a ninja chicken. And it's confusing. But he's also nowhere near my least favorite villager, and I wouldn't hate having him on my island, though I don't think I'd ever intentionally invite him.