DCs are you.

If you have sex with a DC without recognizing that they're you, you're acting out a cheating fantasy and will probably end up hurting your relationship eventually.

If you recognize that a DC is you, your honesty will probably be reflected into a much, much hotter experience, beyond sensation. And when you wake up, you're going to look at the person sleeping next to you with a much broader sense of your emotional connection with them.

There's always the third option of looking at DCs as fake and thus, toys. I don't have much experience with this one, but I can't imagine it being that bad. I bet if you told your partner about it they'd think it was pretty hot, and ask you how they could be more like your dream machine.

One thing's for sure, sex with a DC can be very different depending on how you think of them.