Yeah, I explained the difference in video between the AVCHD and MKV. They use the same video master, but the AVCHD is more highly compressed than the MKV. So literally the only difference is the “blockiness” (compression artifacts) that you deem to be “irrelevant.”

If what you’re looking for is higher resolution (1080p vs 720p), you won’t get it. Despecialized is 720p in all flavors.

Maybe if you described your “gripes” with the AVCHD in more detail we could be more helpful to you.