I’ll try to keep it as simple as possible, but feel free to ask for more details if you feel it’s not enough.
Basically, H264 is far more advanced than any of the codecs we consider “good” for DAW playback. That is why it looks far crisper while keeping the file size considerably small, and its professional name is AVC (Advanced Video Coding).
Because H264 is far more advanced, it also demands far more real-time system resources. Each time you press play or, even worse, scroll/scrab through the timeline, it pushes the system into extreme mathematical calculations, that happens because the most popular H264 encoding is done with what is known as GOP (Group Of Pictures) using IPB, i.e., i-frame p-frame b-frame, the i-frame is a complete video frame (full images). The p-frame (also known as Anchor Frame) and b-frame only hold data that tells the decoder what has been changed from the last I-frame. So a group of pictures may look like so: IBBPBBPBBPBBI but may easily look more like this: IBBBBPBBBBPBBBBI, imagine how many calculations are required just to present the 15th frame in the above sequence (Group Of Pictures).
That’s where ProRes and DNxHD(HR) come into the picture, the industry understood quickly that AVC (Advanced Video Coding) is great as an end product but horrible for editing work as it draws a lot of real-time system resources at the expense of more important editorial needs which leads to audio/video sync problems and stuttering video playback, so both Apple and Avid created their own standards, ProRes by Apple and DNx by Avid. Both codecs are almost the same in their essence, they use what is known as Intra frame compression so they only have i-frames, which means the compression is by far simpler and easily decoded but it uses significantly more disk space to present good quality video.
That’s why they created several “flavors” for their codecs to fit all industry needs:
ProRes Proxy, ProRes LT, ProRes 422, ProRes HQ, ProRes 4444, and there’s more.
Avid DNx has an even larger flavors set but we’ll not get into that.
Professional video editors who rely solely on the picture work with ProRes Proxy or DNxHD 36 through the entire editing process and only render the final product in full quality (H264/ProRes HQ/DNxHR HQX).
So I think it’s safe to say that audio producers of all types can and should work with a little unsharp image to increase their DAW productivity even if it means much more disk space and less enjoyable video reference, that being said, if you have a high-performance SSD and willing to spend the disk space required, you can always work with ProRes 422 or DNxHD 185 for a clear sharp image experience while keeping your system resources free for audio plugins, virtual instruments and other important things we use to produce our product and desperately need the real-time processing free from unnecessary interruptions.