Oh gosh....well which one would be better for the fashion world?
I'd recommend one of the F2.8 versions because you can get shallower DOF with them....but also consider that they are really heavy lenses. The F4 versions are still tack sharp and great lenses.
Having Image Stabilization (IS) is better than not having it. You may not need it if you are shooting fashion in the studio with strobes but when shooting with natural light it can really be helpful.
I've got the 70-200 F2.8 L IS and it's far and away my favorite lens.
Oh are these the lenses that are white? Is there a reason why they are white?
Yes, these ones are white. All of Canon's telephoto L lenses are white. I think the original reason was that white was to keep them cooler when used outdoors in bright sunlight, as too much heat could affect the finely tuned parts of the lens. However, I think a bigger reason they are still white, is that it makes them easily recognizable.
LINK
At first I had still planned on maybe buying these things used to start out but financing is always an option. LOL
These high quality lenses are built like tanks, so they are
usually in good condition when you buy them used. But also consider than some of them get a lot of use and abuse from pros and you may not want one that has been put through the ringer.
Also note that Sigma and Tamron both make a 70-200mm F2.8 lens. Maybe not quite as good as the Canon L lenses, but pretty close and probably half the price.