As with most online discussions of brands, Jaimie, I don't think you're going to get a satisfactory answer here. Both are solid brands, and both have good, better, best lines of paint, so any comparisons need to be between comparable grades of paint.

I've heard Sherwin Williams has good sales, so that might be a factor for you to consider. Or try Benjamin Moore since you haven't yet. My advice in this situation is to go with the store that has the better service or location. You don't want to run out of paint and have to drive 2 hours to get more (I've done a lot of reluctant color matches for people who didn't plan ahead and ran out of the brand they started with).