I was thinking of buying a Canon EF 70-200m f2.8 mk1 (I would love to buy mk2 but here's a noticable difference in price, at least in my country), but after awhile I came to the conclusion that this lens is not as good as the mk2.
People say that sharpness isn't good enough if we compare mk1 with the Sigma or Tamron. So I decided to research the Sigma 70-200 mm f2.8 APO EX DG OS HSM; It appears it's not that bad - maybe not that good as mk2, but...
Then I found the web-site Comparision of image quality
and it doesn't seems like it's that much better, actually it looks like it's softer. Then I read some threads on CanonRumors and found, that people say, that it's probably better to go with the L f/4, rather than the f2.8 mk1, because it will perform much better.
and as you see, I just gave up and came to ask you guys.
Which one is better to buy?
P.S For sure, I would love to have a f2.8, but if this lens such a bad one, and I will have trouble upgrading later on (sell this lens) and buy a better one. Probably it's not that good idea to invest into mk1.