Hi I am looking at buying a 70-300mm lens and my budget is less than $300. I am currently looking at the Nikon 70-300mm G lens and the Sigma APO MACRO SUPER II 70-300mm. Which one will be the better purchase? I have heard comments that the Sigma is better than the Nikon and is more ex. Just want to have you guys' comments on which one will be a better and worthwhile buy? Thanks..