how the dismemberment works is both in the server setting and the client setting.
IE I have played on a few servers since I got cg_dismember to work (BTW once you set it to 1,2, or 3 ETC it stays on so you never have to type it in again, and so long as the server is running dismemberment it will be on too).
In these servers I found that with dismember set to 3 I get the most SP like dismemberment on overage. 1 works but I think that acts more like the normal SP dismemberment (not the cheat code dismemberment).
the main difference between MP and SP dismemberment?
In SP putting dismemberment on will make your saber do more and more damage based on the setting I think. In MP this doesn't happen. A good solid hit without it turned on will do no more than with it turned on.
We all have to die, the only question is... Do you want it on your feet? or on your knees...