I move out the ones I feel neutral about after they have given me their picture. I love Erik, I'm keeping him around until he gives me my picture. Personally, Eugene is my favorite. Smugs are my favorite personality and he's the sweetest most generous one in my game. He's always giving me stuff, inviting himself over when I'm decorating, pinging for me, he asked for 90% of my smug PwPs, and he's always so relaxed cause he's fishing or shopping on main street most of the time. I guess it kind of depends on who you want in the game. Which personalities you favor. Which species you prefer. I always have 2-5 villagers I'm willing to let go after I recieve their picture just so I can experience as many villagers as I possibly can.