I found a few posts discussing these lenses, but none in the context I'm trying to make this decision. Some advice based on my particular case would be greatly appreciated. In the last 5 years I've been trying to assemble a nice set of three zoom lenses that I use mostly for travel photography (and that includes wildlife, street photography, landscape, portraits, etc). After some investment over the years, I now have the following setup: Canon 50D Canon EF-S 10-22mm f/3.5-4.5 USM Canon EF 24-105mm f/4L IS USM Canon EF 75-300mm f/4-5.6 IS USM The 75-300mm is the oldest of the three and clearly the one in most need for an upgrade. My budget allows me to to sell the 75-300mm, get the EF 70-300mm f/4-5.6 IS USM and still have a couple hundred dollars to spend on some wireless flash triggers (I also do some portraits with off-camera flashes). The same is true if I got the EF 70-200mm f/4L without IS, but since I seldom use a tripod when travelling, it seems to me the IS would be important to keep. If I made the jump to the EF 70-200mm f/4L IS, I would have to spend another $350 and forget my wireless triggers. I've learned over the years that a lens is a big enough investment that sometimes spending more upfront saves you money later, avoiding multiple upgrades. However I'm not so sure how much benefit I'll get from each of these two lenses (EF 70-300mm f/4-5.6 IS USM vs. EF 70-200mm f/4L IS). When I look at the EF 70-300mm f/4-5.6 IS USM, I question if the improvement in IQ and IS technology is a large step up from the EF 75-300mm f/4-5.6 IS USM. I'm not at all satisfied with the results I get from my lens, particularly wide open and towards the 300mm end. However, if the difference is not significant, I might just keep the older version of the lens or go for the EF 70-200mm f/4L IS (either now or later). When I think of the EF 70-200mm f/4L IS, I question if the range is right for me. It also overlaps a bit with my EF 24-105mm f/4L IS USM and it doesn't go very long. Since I'm used to the 300mm focal distance, I will definitely be looking at getting the 1.4x teleconevrter down the road and may have to use it quite often. The teleconverter will bring aperture up to 5.6 and will reduce IQ, so I wonder how that setup will compare with the EF 70-300mm f/4-5.6 IS USM. Sorry for all the details and I hope you got to this point. Any advice will be very helpful when making my final decision. I want this to be a long term decision and provide me with good IQ and the range I'm used to having. Thanks, Marcelo.