The A520 has more optical zoom which helps with taking shots further away without degrading the picture quality. And I actually like the fact that the A520 uses AAs because they're easier to find, and it will take any kind of AA you can find (li-ion, NiMH, alkaline, etc...) Furthermore, the A520 would be a better camera to learn on, it has more options located on the camera through buttons and wheels than through the on-camera menus. Finally, the additional megapixel that the SD400 gives will only matter if you are doing an insane amount of cropping (more than 50% of the picture for an 8x10!) or if you want to do larger than a 20x30" print. Here's a few benchmarks for you: 3MB - 8x10", 4MP - 20x30", 5MP - 20x30" (I know it's the same, but that's how they're rated...), 6MP - 30x40", etc... With new cameras and the higher megapixel, all they really give you for the most part is the ability to crop more without risking losing picture quality, or printing out a bigger picture (which would require a photo lab anyway) without losing picture quality. It really does not improve the quality of a wallpaper image or the quality of a 4x6 print or even an 8x10.