4.7 is available in the non-cartridge format, but it is only supported in the newer drives--ie. more expensive ones.
The -r/+rw drives are often cheaper--at least the good ones--and offer more flexbility. DVD-RAM is really only good as a backup medium. Tape Drives are cheaper and just as fast for backup--though they are much slower for restoration.
For making movies and backing up PS2--DVD-R is the best way to go.
If it ain't broke don't try to fix it! But, hell if you can tweak that bastard just a little bit more....hehehe.