I think it depends on what you want out of it, and how you like to work. Two majors equals two sets of required courses, so you might have fewer choices about what classes to take, or it might take more time to get all of them done. Two majors would give you the chance to go fairly deep on two interests; one major might give you the chance to go deeper on one of them. Some people double major to give themselves more job options. If you’re feeling indecisive think carefully about whether two sets of requirements and work are what you want–it can sometimes be easier to change majors than to do two. Talk to your advisor, and to professors in both of the programs you’re interested in and they can give you a better idea of what’s involved and what makes sense for you.