Well, they are so different I do not even try to compare them.
I had some time to try the single cut yesterday, plugged. The sound is just what you want to hear from a single cut, warm and thick and somehow lespaulish.
The 509 sounds are , by comparison, something thinner, a little more treble - ish, even if the neck pups can give a very beautiful hot warm bluesy/slashy (depending of your amp settings) rock sound(s).
The biggest difference is that the single cut(e) is kind of a straight forward rock machine when the 509 needs to be gently tweaked but can give you almost anything.