Why in Vegas Pro Avid DNxHD codec and MP4 H264 - looks similar?
But in AE (as an example) different.

I was making a test for myself but I think for someone It can be interesting.
Video was shoot in Cinestyle and than Technicolour S-curve was applied. Canon 600d

In AE - the difference is visible in the codecs. And what is interesting that in AE original Canon .MOV is better than h264 mp4 (less contrast and more usable), but in Vegas it is vice versa and more over h264 mp4 looks the same as Avid DNxHD in Vegas Pro 11!

Here is a link on a video:

Video codecs comparison in Vegas Pro 11 and After Effects CS4 - YouTube

Thank you for your interest.