I have a dilemma: Which one is better: Canon 28-105mm f3.5-4.5 II USM or Sigma 28-105mm f2.8-4 Aspherical Price is almost he same (250 vs 230 euros). What would you recommend? Which one is: -faster -sharper -nicer colors ? Thank you,. (this is my first dslr, and my first lens, and the top I can afford right now. I will buy EOS 400D. So I am considering only these two lenses, no other is in question right now).