Hello all, I have owned a Canon 100-400 Mk1 since 2008 and I think the years have finally gotten to it. I don't quite have the funds the splurge for the $2200 Mk2 but I can afford the $899 150-600mm Sigma and Tamron models. My question is- are either of these two lenses better than my old 100-400 Mk1 (in terms of image quality, sharpness, etc.)? I am trying to decide if it is better to just buy one of these lenses or keep my dusty old 100-400 and maybe get it serviced. Thanks!