Upload & Sell: Off
Well I'm going to need some convincing here. I've had the Canon 100-400 for a long time, and it's been a nice flexible lens to carry around. Recently (i.e. past few years) it has seen extremely little use. I shoot sports, and it's my only lens slower than f/2.8. When in daylight and when traveling, I do like the 100-400mm range it offers and the fact that it isn't very heavy.
However, I have an opportunity to snag a used Sigma 120-300mm (non DG), and am considering selling the 100-400mm to put money toward it. I do realize it's a lot heavier (I used to work with the Canon 300mm f/2.8), and so weight is not the issue. I'm more concerned with sharpness, contrast, AF, etc. between these two lenses.
All in all, would you keep the 100-400, or sell it and get the 120-300? I could see myself using the Sigma more because of its low-light capabilities, but AF speed & accuracy is not something I'm willing to sacrifice.
**Also, if there have been any past posts on this topic that I missed, feel free to post the link...I don't expect you to write some long post when the work has been done for you already