I like main characters with distinct personalities, but I'm also very picky about their personalities. If a main character has a personality I don't like, I might give the entire game a very low rating.
Personally, I have a hard time inserting myself into the story, so I prefer a protagonist with a more distinct personality.
Also, 'no personality' MCs get boring for me pretty quickly.
I like MCs who have a clear personality, but only if I can relate to their thoughts and values.
If the protagonist has opinions or reactions I can't empathize with, it completely breaks my immersion. A well-written personality is great, but it has to feel natural for me to stay invested.
I like MCs whose personalities I can find connections. It's not that I never self-insert, but having a protagonist whose personality fits the storyline really shapes gaming experience.
I definitely prefer personality. I find that "no personality" blank MCs tend to all be very overly innocent/submissive/meek which I just find tiring, especially when they're meant to be adult women. I love an assertive MC!