Most Helpful Guys
You can't "prefer" one - to be really attracted to someone, you need both.
I wouldn't date someone who I wasn't physically attracted to, and wasn't also attracted to their personality.
Looks is typically more important at first because it's naturally what gets noticed first and guys especially tend to be very visual. But even the most beautiful girl will get very boring very fast if she has a lame personality, no sense of humor, etc.
Basically looks gets you in the race and then personality is what would get you to the finish line.
Most Helpful Girl
Tbh there isn't a absolute clear answer to look or personality, usually is a combination of both for things to work. Let's be very honest, you wouldn't notice a person's personality if you are not even a slightest attracted to their look right. Personality just doesn't get display out in plain site, you have to notice the person to see their personality. And physical attraction is when you start to notice the person.
Younger boys will say look because that's all they see, and as they grow to be more mature, it slightly move towards a balance of both look and personality. I hardly think that there will be someone out there that says 100% personality and nothing about the look.