Nikon 14-24 vs Tokina 16-28 on FF

I am curious about personal experiences comparing these two - not just charts - specifically at smaller apertures for landscapes... Also, for the moment, not taking the huge financial savings of the 16-28 over the 14-24 into account (although I obviously would).  Have read photozone and other reviews, lookign for field experience.  Also curious if people have often come across mechanical (QC) issues with the Tokina...

-TBri