I own a nikon 24-70 and use it professionally.
I cannot recall a single time I need VR for it.
The Nikon is built like a truck and the lens quality is outstanding.
I am sure the Canon is the same.
I do not understand how the Nikon misses focus, as every shot needs composition and in that instant, the lens focuses.
When you spot focus and not have your camera set on 'professional' you do not have focus issues.
The Tamron has an extending pump barrel, a feature that sucks in dust.
A feature best reserved for lower use lenses.
I work in dusty environments so the Tamron would never make my short list.
I am sure the Tamron is a great lens, but not to be carried away by hype from users who may also be employees of Tamron.