I went from a Core2Duo and it the early 2011 MBP 2.2 and I saw a huge difference in all of the above. Compressor screams. I can do VBR m2v encodes right around real time. Saw a great improvement in H264 encoding also.
You can set a MBP to favor performance over battery, and it should be set to that especially when plugged in.
An iMac is cheaper and faster, bigger screen so if you didn’t need portability then it is a better system. But I can say the 2011 MBPs rock as an editing system. My old laptop went done and I needed a laptop more than a desktop so I sold my MacPro 8 core 3.0 (first gen 8-core) and this thing is on par with that system.