They're both important.
When we meet a potential dating partner for the first time, we tend to look at their physical appearance first to decide whether or not we would ever date or sleep with them. Unlike personality or emotional compatibility, it usually takes 3-5 seconds to determine whether or not we find someone physically appealing or not; so it's something that is usually determined very quickly. We either find someone attractive, neutral (neither attractive nor unattractive), or unattractive.
And if we find someone attractive (and sometimes neutral) only then will we take their personality and our compatibility with them into consideration. On the other hand, if we find someone unattractive from the get-go, we will never consider them potential romantic or sexual partners, no matter their personality. You can meet a girl with a good personality and common interests, but if you find her very unattractive, you'd probably never consider her a romantic or sexual partner.
So to answer your question, do looks or personality matter? They both matter.