Okay, err. Let's take this hypothetical situation.
My girlfriend is very sexually satisfying, but she's an absolute b
itch. She's manipulative and plays mind games, ruins my self esteem, and cheats on me. I'm not sure I love her.
My boyfriend is very sexually satisfying, but perhaps not quite as much as my girlfriend, because he lacks things like boobs (not being shallow, this is hypothetical

). He's kind, lovely, treats me well, cares for me, and I think I'm falling in love with him.
Even if my girlfriend is better sexually, I have very little emotional attachment -- yet my boyfriend I have a lot of emotional attachment to. Does that make sense? xD
If you swapped the situations around, I'd have more emotional attachment to my girlfriend than my boyfriend. x)