Video rendering is more CPU intense.. Personally tried that. If you're rendering a very big video, quad core sometimes can speed up your process by hours.
I think those 2 got lot of different is because like Arthun said, GPU you speed up or enhance the process, in this case the CPU is same so it is up to the GPU to decide which is faster.

P.S: So I'm finally back to lowyat.. been on hiatus for months

Outcome will be different.
Work lo.. been busy working.. since now still probation so a lot stuff need to learn