Length of recording affects quality
I got these numbers somewhere:
HQ mode (1HR, 9.5Mpbs, MPEG2, 720x480)
SP mode (2HR, 5.1Mpbs, MPEG2, 720x480)
EP mode (4HR, 2.5Mpbs, MPEG2, 352x480)
SLP mode (6HR, 1.7Mpbs, MPEG1, 352x240)
For me, the breakpoint was 2hr 4min, the real SP max, when going from SP to EP, that the quality noticably dropped. It is unfortunate that a lot of movies come in at 2hr 10min or so. SP does produce a good result, use EP only to get it all on one recording.
I had my first sighting of dual layer (DL) DVD disks at a Wal*Mart but the price was high for a write once. But it would double the times with the right recorder.