Im planning on buying a very fast long telephoto for my sporting events (soccer, baseball, american football) and i am deciding between the Sigma 120-300 2.8 NON DG used or the the canon 300 2.8 NON IS used as well. To make it clear i cannot afford these lenses new unfortunately . This will be a real investment for me and want to keep this lens for at least a decade (ok thats a little long, but i want to keep it a long time). I like the 120-300 siggy as it gives me the flexibility of a zoom, but it is way heavier than the canon weighing 10 pounds vs 6, its image quality is a zoom and although very good, when i go to a 1d or maybe full frame i want to be able to use a tc to gain that extra range. I also have a 70-200 2.8 L and have toyed the idea of picking up another body too, that way i would have a 70-200 and a 300 2.8. but right now im still saving up for these two monster lenses. The sigma is 400 cheaper than the canon right now used and it is a slightly higher condition at keh, the siggy is rated Exc, and the canon is bargain. (according to their scale thats only 1 step apart).
Also will the non dg work on my 7d, will the dg have some compatibility issues that sigma has had in the past? Does canon still accept repairs on the older 300 2.8 non IS.