I like similar interests and hobbies the most. Me and my boyfriend have different personality types in terms of introvert and extrovert but we do share a lot of similar hobbies and interests which makes it great.
I think exact opposites does not help a relationship, but the same can be said for extremely similar people. A balance would be best, although leaning towards similarity. For instance, I like to stay at home and have a night in more often than going out. I love to just hang out at home and spend time with my girlfriend.
Now, if she is more of an out-going type who loves going to the club, that will inevitably lead to conflict. At the same time, there has to be some difference to keep it interesting and fun. If her strengths are my weaknesses, we'd make a great 'team' and couple.