I'm not that knowledgeable about one CPU over another regarding speeds, it was simple with single core Pentium CPU's, basically the faster the chip the higher the gigahertz. Now days with multi cored CPU's I'm uncertain when comparing old with new, I can say that from using Nero to process and author DVD video that my Core 2 notebook is roughly twice as fast as my old desktop Pentium 4, my notebook is 1.85GHz and the old Pentium was of a comparable speed, it also runs games better than the pentium.
I bought a new 2.66GHz overclocked to 3.4GHz Quad core machine last year and it is perhaps twice as fast as my notebook at processing video with Nero.
Put it this way using the old Pentium 4 took 5 or so hours to process a video. My notebook would take around 2 or so hours to process the same video and my new quad core machine takes around an hour or less. Also I'm able to download faster on my notebook and quad core machines than the old Pentium, I was getting 6 Mbit on it and it went up to 10 Mbit when using the multi core machines, hope this helps somewhat.