What do you prioritize in characters

For survivors all I really want is to enjoy their aesthetic. Vee's great for me, I very much like her visuals, and I've played Meg, Claudette, Jane, and Sable for the same reason.

I guess I did briefly play Jill because I like her from RE, though.

For killers, it tends to vary, but broadly I enjoy macro-focused powers with M1 gameplay being at least sometimes relevant. I like Trapper, Wraith, Sadako, Legion, etc.
The furthest away is that I have been learning Houndmaster lately, I like her projectile/dash more than others for some reason. She's dope when she works, though.

For killers I guess it's mostly fun or novelty, and a little bit mobility. I like Dracula and Vecna for the variety of abilities, and Dredge for its vibe. Wesker is solely IP love. He's not a killer I'd play if I wasn't a fan. Michael, I liked Tombstone Piece even though it was super unfair, and now I play Scratched Mirror, which is a hella funny. Clown because the bottles are fun and his theme music is one of my favorites. Plague cause she's hilarious.

I've pretty much stuck with the same survivor consistently, which is Felix. It was pretty much a random choice and now I'm attached. Other choices are mostly for memeing.

I tend to go for licensed characters out of nostalgia. Most of my 100s are licenses from 90s games except for skull merchant, and in her case it was because shes hot lol but that also makes her stand out because most of the games characters, they avoid trying to make them attractive, which was why sable was such a huge seller and her bikini is the most sold cosmetic in the game - every other simsuit has some back piece in the way or still covers a lot etc. And skull merchant's swimsuit was like POW! We will probably never see anything like it again lol.

As for gameplay yea the survivors it doesnt matter but with killers i play the whole roster regularly, ive found the fun in each one. Tho some are more comfortable to use than others like xeno / dracula / nemisis, ive started to enjoy playing krasue lately now that shes so rare people dont give up / dc anymore like they used to so its like playing any other killer now.

For survivors it's quality of the voice acting and if i like their style.

For killers, i'd like them to feel engaging and satisfying to play and ability to achieve max bloodpoints and emblems is preferred but not required. Generally i value mobility on killers a lot because it makes them versatile, and i like some chase lethality. I also like atmospheric and thematic killers. Also i like killers that have a variety of fun add-ons, this is very important because it contributes their longevity and worthiness of p100'ing.

For Killers, I prioritize their ability to counter the main thing standing in their way, but in a gameplay loop that's enjoyable for me. After trying 15 different Killers, I came to love Nemesis the most. He has a fun and dominant power that lets me deny opponents resources, and the two zombies feel like a reliable radar.
For Survivors, I prioritize design. I'm drawn to characters who look authentic to surviving in the realm. Since the RE characters have already been through hell and survived in one piece, they're my favorite to play as.

For the survivor: Cosmetics I like to look at because I'll be the one looking at them. How they sound, some have a super annoying scream or are too whiney when injured. If they have voicelines, while the voice lines can be amusing most get annoying pretty quick so since I can't turn them off I just don't use the character.

For killer: I go for who has a power that is simple on console and I have fun with. Trapper is my favorite, I enjoy finding random places to put my traps down to catch survivors. Easy BP gains, Doctor is my go to for this because it's easy for me to get BP in all the categories and bonus enjoyment hearing survivors scream throughout the match. Voicelines and noises they make throughout the match. I don't like them being chatty and making comments, some just sound annoying when stunned or using their power. Ghostface being silent and letting out an annoyed sigh when stunned is perfect.

It has changed over time. I used to favor killers with more skill-expressive powers. That was back when I could play the game for 20+ hours a week.

I focus more on macro oriented killers now. Condemned Onryo, Knight, Trapper, etc. The game sense never really leaves you, and I don't have to worry about honing power mechanics. I often do better with them than I do with more mechanical killers anymore.