AMD's VCE encodes frames significantly slower than NVENC and QuickSync. I don't know about compression efficiency/image quality though..
While my (HD4000) quicksync can encode 1920x1080 frames at 130+
(HD7850) VCE struggles to pass 40.
The two are set to best quality preset @ 20mbps.
I used Msi afterburner for benchmark since it has support for hardware h.264 encoders.