It's a little bit like comparing apples to oranges. On the one hand, masturbation allows you to touch the parts that you know will give you the most pleasure while a sexual partner might not always get it right. On the other hand, sex involves intimacy and closeness with another person, which masturbation does not. If you're going for a quick orgasm, masturbation is the more efficient option. If you're going for long-term warm, fuzzy feelings, sex is more likely to bring those on. Unless you're talking about masturbating next to your partner, then ta-daa, you might get both the orgasms and the warm fuzzy feelings.