Got both. The 5D wins hands down on everything except: sensor cleaner - the 40D has this and in my experience it works reasonably well; live view - if this bothers you - in my experience it's less useful for precise focusing than the type S precision screen plus angle viewfinder. But the standard focusing screen as supplied with the 40D is too coarse to allow for manual focusing. The standard screen supplied with the 5D is better but I think it's just because the viewfinder magnification is less. The 5D vf is, IMO, good (though less so than the Oly OM1); the 40D vf is usable rather than good. I've simply never used burst mode so the 5D is plenty fast enough for me. The 40D is much more convenient when used with long tele lenses but this is a matter of size/weight/cost of the lenses traded off against image quality. And this to me is the numb of the APS-C/FF debate. When used with "normal" lenses (wide, standard or shirt to medium tele) there isn't even a significant saving in size & weight, though it may well be true that the FF cameras require better (therefore more expensive) lenses to realize the benefit of better image quality.