Noise levels are better on the 50D if comparing images at the same size of the 40D. This is a fact so basically the 50D handles better noise than the 40D at the same MP or Resolution level, if you compare both camera images at their original Resolution, yea the 50D will be noisier but for such a small margin that it is almost pointless to discus. Like I said if you can afford it buy the 50D if not buy the 40D the 40D is a great camera just not better than the 50D but it will be capable of producing the same quality images as the 50D but with a little bit more of work, Like I mentioned before the 50D makes everything easier. One of the big differences I love about my 50D is the way it can handle exposures, before with my 40D I would have many pictures underexposed or overexposed but with my 50D everything is almost perfect all the time, AF is also better on the 50D, with my 40D I would get out of focus images many times, with my 50D 99% of my pictures are in focus, I only use center focus the same I did with my 40D but the 50D seams to focus better than the 40D. I find the upgrade value worthwhile for these and many other reasons, if you like to do more pp then get the 40D if not then get the 50D.