For us it’s an individual choice. We are in this to allow the other to experience and fulfill their fantasies. When one half of a couple starts interjecting their attractions on their significant other they will find that this whole thing will go south in a hurry. In our case she has sole choice of who she has sex with, and I have sole choice on who I have sex with, and we do our best not to be judgmental about that choice.
Now that’s not to say, and it rarely occurs, but if one of us has negative personal information concerning a person that the other is considering being with we will inform them of that information. But that is limited to something that the other doesn’t know about that person. As far as physical characteristics, age, or appearance, that would be solely up to them.
The adage is that beauty is in the eye of the beholder. Unless you want her to start picking the women that you can be with, don’t pick the men that she wants to be with. Swinging is about open and honest communication, if you start criticizing her choice of playmates, you will soon find her unwilling to share her fantasies with you or to take part in this with you.
As long as my wife is safe, as long as she’s engaged in something that she wants to be engaged in, with a person that she wants to be engaged with, the choice is hers.