For me, the benefits...
Each romantic relationship I have had has been very different from the others. I miss some aspect of pretty much each of my previous relationships. What poly lets me do is have more relationships at once, and can therefore experience those differences, without having to "give up" an aspect of them.
I love to love, and be in love. Having two people in my life allows me to be MORE in love, and be loved more, too. We look out for each other, too, so there is a level of support structure there which couldn't be equalled by less close friends.
I can explore more of my interests, because I have more folks to share them with. Again, something I could do with friends, but doing it with someone you love makes it that much more special.
The other one, I suppose, because I feel that I am "wired poly" it lets me be me. I was miserable trying to be monogamous, and those that loved me kind of knew it.
@QuestioningMono: I have heard similar things to what you wrote before. I am the poly part of a mono/poly relationship (my mono partner is not on here) so have asked her in the past what she gets out of it. Her answer is that she gets to be with someone she loves and cares about and can see that this poly relationship style makes me happy. I have asked her before whether she would be happier if I were monogamous, and she said something along the lines of "yes, of course, but you're NOT, and I don't want to change you - you are who you are. I certainly wouldn't want you to ACT monogamous because I know you would be unhappy." The activities of working through our poly-related relationship issues has actually strengthened our relationship (which has lasted nearly 20 years now) and given us much better tools for us to deal with the everyday issues that come up. I think that we have more quality time now than we did when we were "monogamous". I won't pretend that it's all "up-side" or a bed of roses, but we make it work.
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