Dedicated 20 amp circuit. 10/2 or 10/3?

Dedicated 20 amp circuit.  10/2 or 10/3? 


10/3 (plus ground) will get you 2 circuits.  10/2 one circuit.  one is probably good but it might be nice to have a second circuit.  Of course both circuits would share a neutral which some will say defeats the purpose.  

Bottom line, if you need one circuit, 10/2 plus ground.


Ok. So each dedicated circuit should have 10/2. 
I watched ps audio run 10/3 and said they were doing a double ground?