a male POV:
looks do matter to a degree, if her looks or behaviour is repulsive, i'd still turn them down. If shes average looking and has a very positive attitude, then i'd inevitably find her cute. Some girls don't look much, but when they smile everything changes.I go with my gut. If i have a good time around her or enjoy chatting with her a lot, i'd fix up a few dates and get to know her better. As long as her face isnt fubar, generally your personal perception of her beauty will change the more you like her. Her character on the other hand isn't up for you to change.

TD:DR - You can at least have a relationship with a virtuous manatee, but you'd never be able to get past a one nighter with a smoking hot hollow flower vase.