Personally I'd just get the F4 version. Sure the f2.8 might be 1 stop faster (not a huge deal) but at F4 you're much more likely to get a shot in focus than f2.8.....especially if your camera doesn't support MA. I've seen comparison images of the F4 and F2.8 on neilvn.com's blog and the difference is bokeh is truly minimal.
The only way that I'd get the 70-200 2.8 is if I was on full frame and/or was making atleast 60K+ a year from shooting weddings and anything else involving people.
The 135 2.0 is an interesting lens though. It will have better contrast, saturation, and bokeh than the 70-200 at 135 but it still won't have the same compression that the 70-200 has at 200mm.
So with that being said I'd get the 70-200 F4 IS as it's a way better value than the f 2.8 and I generally stop my lenses down to 3.5-4.0 anyways just to increase the odds of getting the subject on focus so if you're not using a top quality DSLR that has MA the 2.8 is a waste of money in my opinion as in a situation like that you'd want a body that can focus consistently at f2.8.
Heres the blog where he compares the bokeh of the 2.8 to the 4.0. As you can see there's almost no difference. http://neilvn.com …/depth-of-field-aperture/
Even shooting my 17-50 2.8 theres almost no difference between 2.8 and 4.0.....I only use 2.8 as a last resort for low light usage whereas 3.5-4.0 is better to maintain a nice bokeh while also raising the contrast/color/decreasing the CA and increasing the chances of you getting an in focus shot as the focal plane is larger.
TLDR; If you're a paid pro getting paid a good amount of money with your photography and you have a good body that is capable of MA and is very good at focusing get the 2.8, otherwise get the F4....the differences between the two are minimal but the F4 version is lighter and gives way more bang for your buck....in this case $1,000 savings bang for the buck.


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