Just to have a point of reference, I ran a recent OpenCL benchmark posted on Phoronix.
Keep in mind the major gap in hardware specs here. We're not just seeing a GPU vs GPU comparison. This is more like a systems comparison since I'm on a pretty old AMD system while the Phoronix test was on a Ivy Bridge system.
Prey doesn't look like it ran nicely. I got a weird 5 fps score. The Quake 4 benchmark didn't run at all.
Here's one from LuxMark. It's one of the better performing tests
The full test results can be found here.