I went through this decision a month ago, i bought a 70-300nonL with my 7D last september, if you upgrade your body to the 7D or 5D2, the fuzziness at 300mm will show up a lot worse than on the 20D. (although i'm still wondering if my lens was just a really bad sample). Check out some pics i posted in the lens gallery
Basically, when i replaced, i looked at every canon in the range and compared them:
- 70-200 f4 nonIS â‚¬5-600: good and cheap, but i really like IS.(which is why i didn't shell out the extra for it in sept). Also, i wanted the extra reach. Also not sealed.
- 70-200 f2.8 nonIS â‚¬1000-1100ish: really good IQ and wide aperture, but no IS or sealing.
- 70-200 f4 IS â‚¬1000-1100ish: apparently one of the sharpest zoom lenses you can get these days. I did read somewhere (TDP or Photozone probably) that the 70-200 f4 IS + 1.4x TC (ii or iii) were a tiny smidge behind the IQ of the 70-300L. Also, unless you have a tc already, add another â‚¬300 or â‚¬500 for a ii or iii t/c and you've spent a (bit) more than the 70-300L. I'd also rather leave one lens on than mess around with t/c swapping, by which time the subject might be gone.
- 100-400L: â‚¬1550ish: I've never tried the pushpull, some people have strong opinions either way. basically from reviews i got the opinion that there was nothing wrong with the IQ or IS, but just beaten by the 70-300L. i decided against it just based on weight/size/extra â‚¬200/older IS.
- 300mm f4L: another option was keep the 70-300nonL for the 70-200 range and swap to the prime to get usable IQ at 300mm. decided against this based on weight and swapping annoyance, versatility of a zoom, and photozone said the prime IQ was about the same as the 70-300L @300mm, but you do get an extra 1-stop.
- 70-200 f2.8IS ii: i'd have got it if i could afford â‚¬2200.
- 70-300L: which i ended up with for â‚¬1350. I don't mind the 'slowness', it's the fastest of any comparable variable zoom for each focal length (except the 100-400 stays at f5 longer). It's shorter and lighter than the others, the IQ is really great, the contrast and saturation are amazing. I've handheld 300mm at 1/15s for really sharp shots (even some at 1/10s but didn't keep them all). can't use with canon teleconverters, i've heard you can kenko 1.4 t/cs, but i don't know which type (mc4, mc7, pro300, some report different apertures to allow autofocus) and i don't know about the IQ (but i'd be guessing just a bit below the 100-400 @ 400).