The EDID override is preferred.
You can easily uninstall the EDID override:
- Go to Device Manager
- Monitors[Expand]
- Right-click on the override
- Select uninstall
- Tick on "Delete the driver software for this device"
- OK
- Reboot
To elaborate on your question about "incomplete EDID":
- The monitor architecture of Windows is not adapted to HDTV. A typical PC monitor information can be fully stored in the EDID base block (first 128 bytes). With HDTVs an extended block (128 additional bytes) is required to store more HDTV timings, audio block, and colorimetry. AFAIK the "Generic PnP" default monitor driver will only accept standard PC monitor timings i.e., it only detects "PC monitors" and thus, any other EDID detection is the full responsibility of the graphic/audio driver (ATI in this case), and here is a first source of "bugs".
- OTH, not even 128 additional bytes are enough to store all needed information. If you add an AVR/AVP to the HDMI chain you'll have of course 2 full, corresponding 256 byte EDIDs. The AVR/AVP EDID has its own plethora of video timings which may or may not collide with the HDTV timings. You would assume that the AVR/AVP EDID processing would be so smart as to simply build-up a "real-time" EDID with the combined video specs from the HDTV + its own audio specs, right? Well, no!
The AVR/AVP can happen to send its own EDID (base and extended blocks), just ignoring the critical video specifications of your HDTV. Have yet to investigate this matter further but reason could be a mismatch in the EDID base block structure, and specifically the relative position of the Monitor Descriptor within the Base block. If Base block structure is the same it is passed through (but not the Extended block) with changes only for Vendor & Monitor Descriptor. In such cases you'll have pretty much no issues, but otherwise - and projectors are a typical case - you'll have video issues with video timings and color specs of your HDTV not being passed through to the HTPC.
So what to do? You guessed it, right?

For here comes the EDID override to the rescue, which Microsoft so generously gave us as a
feature of the OS since Vista

. WIth this new feature you can custom build your own EDID. And here are two very easy directives to follow for a quick workaround:
- Try to put your favorite/preferred video timings in the base block (in the Detailed Descriptor Block specifically), as graphic drivers are still PC-monitor oriented. You'll have room for 2 descriptors mostly, which is plenty as 1 native resolution is typically used.
- If your graphic/audio driver is screwing up with audio detection, well just find one HD audio block that it can parse (this has been the solution for bitstreaming) and stick it in the extension block (the audio descriptor specifically).
So you can realize, the EDID override is not just an option, but THE solution for what is really an intrinsically flaky interface. You will "see" that your edid info is not fully detected when you run into video issues as described in the OP, or when you only get 2 channels instead of 5.1 or 7,1, or you can't bitstream as with the issue of this thread.
You could compare anyway the real-time EDIDs base blocks captured by directly connecting the Display Device and the AVR respectively with the registry value showed by moninfo (only 128-byte base block), and use
Extron EDID Manager to analyze it.