the 300mm lens would get the longer shot than the 200mm - however the edges of the 200mm shot would be missing (because its on the crop sensor camera) and thus it would look like a longer lens had been used to reach that range than has actually been used - its good as it means you can remove a lot of edge space in a shot which might be wasted (hence the idea of it getting closer than a full frame camera - where you might have to crop a lot of the shot for wasted space. If both cameras are 10MP the crop sensor has the advantage if you not using the edges much (like in sports or wildlife where your always zooming in closer) and the image from the middle of the shot is placed onto the 10MP sensor - whilst the fullframe camera will reocord all of the edges that you don't need and cropping will result in a smaller overall image. Were the fullframe camera to be something like a 20MP sensor then the cropping problem is reduced since one can remove a lotof the shot and still have a large shot to work with.