What should you do if you like a girls personality but you don't like how she looks?

I feel like the biggest, most shallow d**che ever for asking this question, but it's been bothering me a lot. So there's this girl I'm really good friends with. We have a lot of the same interests and we're generally similar people. I have no doubt that if I ask her out we would have a very long, good relationship. The only problem is that I don't find her that attractive, and most of my guy friends agree. The thing is, I don't want to date a not so great looking girl and miss out on this other girl who I don't have so much in common with, but who's a little better looking. It's not that the not so looking girl is really ugly or anything, it's just that she's a bit taller than me and is built kind of awkwardly. She's really cool and I think a relationship could be awesome, but I feel like I'd loose interest because she's generally not good looking. This really makes me feel like a bad person... So should we go out or stay friends? I know that she'd be cool with it either way.