Deal With Unregistry or GoDaddy?

There is a domain name a client wants me to obtain for them. It's available on Godaddy with a buy it now price and on Unregistry with a request for price form. My question is which would be the better avenue to negotiate a price for it?

I know Godaddy owns Unregistry now, but with your experience, which is typically better to negotiate with?

I thought about filling out the form with UR and calling GD at the same time, but think that might not be cool to do.

Would appreciate some advice form this community.