I have both the 70-200 F4 and 70-200 F4 IS. The non IS was my first L lens and it's quite spectacular in outdoor stuff. I got the IS version as I also like to do low light work and it's also great. If you can afford it, the IS gives you more flexibility for low light shooting. I don't have the 2.8 but I believe it is about the same size as the 300 F4L. That's also a nice lens but it's big and not fun to pack that around all day and if you want to be discrete taking pictures, it's a conspicuously large lens to point around.