It should also be noted that the video editing software in question must specifically support Quick Sync. Quick Sync support requires the use of a custom intel API. intel's site
has a list of video editing tools that provide support for Quick Sync. (It may not be an exhaustive/regularly updated list, though.)
Yes, very important, I forgot to mention that. By the way, here
is another article from tomshardware that delves deeper into transcoding/image quality using quick-sync, AMD app, and Nivida Cuda. Its probably the best article you'll find on the subject.
Their conclusion, it really comes down to which software you use paired with your hardware acceleration of choice. I highly
suggest reading through it. In the end, if you want the best image quality, you'll have to keep encoding on the cpu only without any acceleration. (that also takes the longest though) In the end, I still say that quick sync being the fastest is your best choice as long as you pick a program that supports and works well with it.
Main: i5-3570K, ASRock Z77 Pro4-M, Asus GTX660 TOP, 500GB Crucial BX100, 2 TB Samsung EcoGreen F4, 16GB 1600MHz G.Skill @1.25V, EVGA 550-G2, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Crosley D-25 Case Mod