70-300 IS, or 70-200L....?

Is there a huge difference between the Sigma 100-300 EX IF DG and the EX IF...? Presumably digitally optimised but how will that effect shots? There is a £100 price difference! Also the Sigma has no IS...which is what draws me to the Canon...

Having abosolutely no idea about Sigma lenses and only knowing what people here say about the L lenses (which is like never bad) you have made the choice harder....lol....anyon​e any examles from the Sigma?

Oh yeh, theres a picture of the Sigma lens and it has a tripod mount, this mean its a heavy mother?

I have the 70-300 IS, and I love it, for a tele, its not overly heavy and it is built pretty darn well. I tried the 70-200 f/2.8 before I bought it, and while I loved that lens, I couldnt justify it with my limited photography experience. I can definately recommend the 70-300 IS. It isnt an "L", but it is a very fine lens for the price.

70-200 f4 L unless you can save for the 2.8

My only quibble with the 70-300 IS is that it isn't full-time manual focus. As far as image quality it seems very good.

The 120-300 that jojo mentioned is better than any of the other lenses mentioned here. Though a heavy beast, it's a constant 2.8 and is sharp,sharp, sharp. I want one very badly for football and baseball.