I already have a 40D. I need full frame so that my 17-40 can give me great looking interior architectural shots for work. If I have the option to get a clean used 5D or 1Ds II, and the 1 series is nearly the same price, at least within about $200 or so, which one should I buy? On the surface, the 1 series seems like a no-brainer, but it seemed so obvious that I thought I may be overlooking something. I had a 5D in the past, and it was a great camera, and is still looked upon favorably. What is the smart move here? Right now, my only lenses are a 17-40 L and a 28-135 kit lens. I plan on a 70-200 2.8 II L as the next lens, and any of those will also work fine with my 40D, so there's no decision about buying a body that's right for a lens, or vice versa, if I had EF-S stuff.