I was about to post this exact question.
I have a profile on PoF and OKC. So far, OKC has been the more successful, with the whole question system, and the fact that the profile settings allow for the flexibility.
So far, I've met and moved on from one relationship started on OKC, and PoF has been a quiet, silent disappointment. As an example, if I look in my city within 100km, for ANYONE into poly, I get zero results. No matter how I type it. There are people on there if I remove the distance specification, but the number is waaay low.
So yes, we need a poly dating site. This polymatchmaker thingy is new to me, so I'll be trying that.
I have many in my family. And this is good.
I have many friends. And this is good.
I have many teachers. And this is good.
I have many loves. And this is a great concern. The greatest insanities of this world are those stock full in the face of all.