While the 5D may be cheaper than the so-called Pro level, the camera is more geared towards the Pro end than the 20D (or 30D) with fewer dials but more Features. Others cover some other areas so I'll try not to repeat myself. Full frame means a lot to me. I like to print large images and use L or other high end Canon lenses (with a few imitations). There are no compromises in terms of weight or compactness. The truth is I prefer newer glass that isn't designed for a smaller sensor. I really liked the 20D and switched most of my gear to the 5D. Now I have three cameras using the same memory card and battery. The 5D feels sturdier and looks more durable than the 20D while being very compact. But pictures? Big. The 20D was and still is a top notch camera at 8.2 and its ability to use all Canon lenses plus the EF-S for a smaller digital image. One person mentioned slowness compared to 20D. I don't agree with that, but it doesn't matter to me. I usually use the drive for on-the-fly bracketing, but almost never for anything, just for quick succession like sports. I had Motorr drives when I was a pro in the 60's and 70's and they have their uses. Sometimes essential. But they're like autofocus. Sometimes you have to be manual. Whenever possible I prefer single shots or in some cases three shot bursts. I find I'm less likely to miss what I'm photographing. The "decisive moment" when driving a car all too often falls between the frames. But there is something for every taste. I'm really impressed with the camera and after trying it out I'm looking forward to riding a reliable 20D as my second camera.
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