So I get .38 at shutterstock and .27 at Bigstock. I'd remove my port from Bigstock if someone could prove to me that I'm losing Shutterstock downloads over this. There's just no way to know.
I could spike my Bigstock port, but I believe all that would mean is that someone who would have bought my image on Bigstock will just buy someone else's image on Bigstock. They won't magically see my images aren't on Bigstock anymore and go buy it off Shutterstock instead.