I've never seen a great zoom beat a great prime. I doubt it will ever happen.
I personally refused to use a zoom until 10 years ago and I finally succumbed to the dreaded 'lazy photographer' syndrome. It's hard to go back to having to move in or move back a few feet when a quick flick of the wrist will do it for you.
The honest truth is that in most cases I am thrilled to go through a wedding (or any assignment) without the constant changing of lenses or juggling of cameras. DLSRs make that an even greater problem with the added risk of dust getting onto the sensor.
It all depends upon what you are shooting. Back in my RB67 days, I left my favorite portrait lens set out to gather dust on the front element. It made a perfect 'soft focus' effect I loved.
Often tack sharp is not desirable.