So you have a DSLR and want to buy a new lens. Of course there are gobs of lenses out there. And a gob of manufactures that make gobs of lenses. Basically, a lot of choices.
The folks at Crisislab have experimented with the workhorse lens of the photographer (24-70mm f/2.8) and compared four brands side-by-side.
These lenses are not cheap, but they could really improve your shots. And if you are looking to upgrade your DSLR, a new lens is usually at the top of the list.
These guys do a great job of comparing the lenses not only for still photography, but also for video. Which is important because so many people are using DSLR to shoot HD video.
Spoiler: They don’t even pick the Canon or the Nikon. They choose the Tamron! The deciding factor was the Optical Stabilization on the Tamron. Spoiler 2: They destroy lenses with baseball bats!