I was going to say!!!
To get such bad results with CMC and Mitsubishi, there must be something wrong somewhere -- both discs are perfectly capable of being burned with no C2 errors.
In fact, I have to say that I come across very few CDRs that won't burn well at their stated speed on at least one of my burners (well at least good enough to read back with no C2 errors anyway) -- which removes the discs as the culprit. Problems like this are 99% of the time due to the writer.
An example -- a friend of mine with a Plextor 24x burner was complaining about some Postech 24x media that wouldn't burn properly. They burned fine at 52x on my Artec and LiteOn 52x writers. He still wouldn't have it though that it was his burner at fault. "It's a Plextor, blah blah blah" <sigh>