Tokina 10-17mm fisheye vs. Sigma 8mm circular fisheye canon

[shortpballer]

I currently have a tokina 10-17mm fisheye. I am considering selling in order to buy an 8mm sigma fisheye. I am considering this because I already have the wide angle taken care of due to my tokina 12-24 super wide. I feel that the tokina fisheye versatility with the zoom feature is pointless, and the 8mm would just be better on the fisheye end. Can anyone tell me if they have heard anything good or have any pictures taken with the 8mm sigma fisheye.

Would you guys recommend against or for selling my tokina and buying a sigma 8mm?

Any comments would be helpful.

Thanks,
Eric