Best fish-eye for crop sensor?

[fenderphoto]

I have a Canon T3 and I'm thinking of getting a fish-eye lens. My only problem is the crop factor. I have used a Canon 8-15mm before and I noticed that under 10mm I start seeing the black ring from the lens. I am thinking of getting either the Rokinon/Samyang 10mm or 12mm lenses. Please help me decide.

 

[mattcantsk8]

The rokinon 8mm works nicely on the cannon aps-c bodies with out any extream vignette