Would I benefit from studying abroad?

I'm an American undergraduate English major who's thinking about going for a Ph.D. Because of the way my university's exchange program is set up, I could go abroad for a semester or two for little additional cost. The thing is, I'd probably have to give up my additional major in chemistry to do so. My school has great science programs, but it is lacking in the humanities department.

Would going to the U.K., or possibly Ireland, to study literature really make me more competitive, or would I be better off with the additional major?