Does technique come easier to sopranos than to mezzos?

I've been wondering this since the upper register, vibrato etc. seem to come sooner and more naturally to sopranos at my school whereas mezzos (myself included) seem to be struggling with their technique for longer. I've been thinking it's due to the fact that sopranos spend most of the time singing in their head voice while for mezzos it's their chest or mixed voice and thus accessing the head voice (and upper register) is not quite as straightforward. Any thougths?