So what DVD R's seem to work better with the plextor?

Are you talking about which format (+ or -) or which media brands? Either way though, this does belong in the media section.

I reckon, moving it there now.

Also how exactly would you know that it was working better? By testing it in another drive? If so then how do you know that it works better in that drive because that drive prefers +/- or that it is because the Plextor prefers +/-?