If the new recepticles are part of a multiwire branch circuit then pigtailing the neutrals is requried. You would also pigtail if there where more than two wires you needed to tie together at that box. Otherwise it is not required. Some will suggest that it is better workmanship to always do so, but life jpoffer above, I find they're arguments unconvincing.
I personally like pig tailing, but as long as you use the screw terminals, I don't see a problem with the other. Do not use those trash stab in holes on the recepticle, they are good for nothing but trouble later on.