I have written from a CD to CD one time with Nero and it was fairly easy and had no problems. This is supposed to be the fastest of the various ways one can write to a CD. The Nero manual indicates that problems can occur when the burner runs faster than the source drive. I subsribe to the Association for Recorded Sound Collections email list and have profited from the knowledge of people with experience in the field of preserving recorded sound. One of the things that came up in this List was that the optimum recording speed for archivists was 12x. This was supposedly due to the various speeds of the drives at work in the process and the fact that disks recorded at one speed at the outer edges and another speed at the inner core. Another factor is the quality and construction of the disk. Some disks are technically inferior and errors will occur.   Mitsui who makes the Mitsui Gold Archive CD-R which is preferred by many archivists recommends a 12x recording speed for the Archive quality disks.

Recording from the Hard Drive takes a little longer because one has to rip to the hard drive and then to a CD-R but is also supposedly the safest route to take. The stability of the hard drive is probably a factor.

Anyone interested can find the ARCSLIST here:
http://www.arsc-audio.org/arsclist.html