Id be impressed seeing someone get 100+lbs dbs in both hands in place while standing. 1db, no problem, 2, no idea how you would do it.
Its not like your feet are floating either, you are going to be driving into the ground at all times like in a bench press if you are staying tight throughout the lift.
Yes, less big muscles are being used, but your also using alot less weight. I think there is alot of concern over something that is not that big of a deal. Have you ever legitimately heard of someone hurting their back from an overhead press while seated?
BB, I do prefer standing because I can use more weight.