I eagerly swallow if a guy cums in my mouth, but still much prefer that he cums in my pussy.
Two reasons. The feel of his ejaculation adds to my orgasmic pleasure. Second, the knowledge that even after I've totally cleaned up down there, a small living part of him (along with that of another man, sometimes two) is still swimming deep inside me and will be (albeit fruitlessly) for several days, searching for the prize. Except for times when I've been away from home for an extended time, that has continuously been the case, ever since I started having p-in-v sex.
Cum to me isn't just a white blob, it is a living collection of a man's half of sex, which I am hosting inside me. I find that thrilling and satisfying.