"(1) First of all, in your marriage, it is extremely important, how your spouse looks. Now, In General, if your spouse is from a higher caste (compared to yours), then he/she will be generally better looking compared to you. If he/she is from a lower caste, then he/she will look inferior compared to you (in general). In first case, you are not able for your spouse. In second case, your spouse is not able for you. So for optimality, we go for our own caste (or a caste close to our rank).Surely there are exceptions, but still caste helps us to refine our search for spouse."

You'd be surprised to meet the ugly Brahmins I know. I find people in lower castes more attractive actually. Haha. I know you've mentioned "in general" but even generally, I dont think upper caste people are better looking than low caste people