The SL versions add AutoVelocity which changes the attack and release somewhat.
as far as i know the the audio path is the same its just the control that differs
there was an upgrade you could add to the non SL version and you the switch AutoVelocity off internally if you want to keep the original attack and release.
you can download the white paper from dbx that will tell you more
dbx® Literature Downloads
As for if its worth it i have no idea, i would think it would come to personal preference.
Blacky did you find out how much of difference there is between the 160SL and 162SL?