personal experience since i used both canon 24-70 mark 2 and tamron 24-70 f2.8 VC..
seriously... i don't c much diff comparing both lenses in term of opitical.... though i do agree that corner sharpness may b lacking a little but it doesn't affect much... (i really mean that it doesn't differ that much unless u r insane pixel pic dude.... but pls.. if u wanna pixel pic.. jolly welll print it out n hang the pic on the wall... else is a wise of time to pixel pic to the huge extent.. lol!!!)
btw... if u r like me who prefer to shoot wider angle and crop during PP, slight soft corner wouldn't b an issue!
btw, the color produced is sweet and lovely
build qualirty.. tamron is sturdy.... no complain for me..
Canon lose out quite badly in term of the image stabilizer.... i could shoot at 1/30 or 1/15 during low light situation!!!
loving it!
use it on the video mode and you will love it further.....
NOW.... the main con to me will be the Hood and the focus speed..
The hood doesn't lock in place but then to say, most of the time i don't shoot with hood (is a trouble when need to switch lenses... we r blessed with hand that can shield light if situation requires the hood... but really la... how often you kanna the reflection of light?!... hahaa)
as for focus speed, at times may require to de-press the shutter button the 2nd time to lock focus during dim/poor lighting (for this area, canon 24-70 mark 2 might be slightly better. BTW... i used both lenses on 5dm3)
if u r not into sport photography or anything of fast pace, it won't be an issue at all..
btw, de-pressing the 2nd time prob cost u 1 sec.. hahaa... small issue la..
for the price i paid.... i love this lens...
during the time when i own both canon n tamron.. actually i used tamron more too!
the VC and optical really win me over and for the price tag, i prob won't cry out tt longer if i were to drop tamron than canon.... LOLxx