Which Urchin should i have?

[howdy20012002]

I am bringing in pencil, pin cushion, short spin urchins with my next shipment.
My questions is which one should I put in my sea horse tank?
Is one better than others for cleaning?
Just looking for personal experiences from people about urchins.
I don't have any corals that I am worried about in this tank so them knocking anything over isn't a concern...
I am thinking the Pencil simply because they can't stick the seahorses with their spines.
Any suggestions?