This project's estimated task run time is interesting. For example, my Intel Q8200 @ 2.33GHz running Win 7 64bit downloaded two tasks. One says 57 minutes the next says 47 hrs 47 minutes? The 57 minute task is being crunched by the GPU, the other task by the CPU.

Conclusion: the GPU is 50x more efficient at crunching the Collatz tasks.