There is definitely a lot going on during a standing press.
Being seated, with a little back support makes it easier to maintain position and focus on the shoulders.
I guess it comes down to if "Pressing" is a means to an end, or the end itself. Every strong MF'er I can think of had/has big shoulders. Some guys stand, some guys sit, or go behind the neck, or do lots of delt raises.
I think I'm going to be a rebel bad-ass, disregard any information that doesn't back up my opinion, and focus on seated dumbbells for awhile.