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Many AMD fans have actually tried to defend the Bulldozer for it's video encoding performance.
However I have just three words for those people: Intel Quick Sync
So in short, the Bulldozer is a complete waste of time and money in pretty much every practical application. So go with what MMJ said and buy a 2600k.
The i7 2600K should be ahead,although the OP can have a look through the reviews in this thread:
http://forums.overclockers.co.uk/showthread.php?t=18328158
They test a varity of video encoding and rendering applications.
A few words for you: its lower quality.
I have tried it at various settings myself and CPU only encodes are still better quality overall. It is much faster due to the use of dedicated hardware in the IGP.
This is why I am after a Core i7 2600 or Xeon E3 myself. If you want maximum quality encodes a fast CPU is the way forward currently.
Intel is not going to make Quick Sync good enough quality so it competes with the six core Core i7 CPUs. Technically speaking Quick Sync would render them bit pointless for video encoding as it is faster.
However,it doesn't. It would also make the i3 2105 a better value choice than a Core i5 or Core i7 for video encoding but it doesn't.