Går inte att jämföra dem så enkelt.
Beror ju helt på vad du ska plåta.
Om du har råd med de dyraste l-objektiven så kan du satsa på 5D, annars är det bättre att gå på en 40D och lägga resterande pengar på bra objektiv för just 40D.
En god vän skrev just om detta så jag kopierar in hans text...eftersom jag håller med fullständigt.
The full frame basically means that you will use an 85mm F1.2 L (R21000) lens where previously you used a 50mm F1.4 lens (R4000). Sounds simple but the min focal distance of an 85mm is too much so you end up buying the 135mm F2 (R10 000) as well....so in financial terms you end up spending a LOT more money to be happy. You may also need the 50mm F1.2 L (R19000) depending on the size of your studio.
Why do you need these fancy lenses you say - simple....the amount of light coming in the lens and the size of the pic potrayed where the sensor sits doesn't change BUT the smaller sensor only uses the centre of that light(pic) i.e. the best bit whereas the full size (larger) sensor uses more of the pic and get closer to the edges . The edge of the light coming into the camera is where the cheaper lenses fall down and therefore the full frame sensors emphasise this weakness.
Therefore the full frame just demands higher quality lenses which cost more to produce.
So......don't look at the cost of the camera....look at the cost of the whole system. A full set of zooms plus 2 primes and the camera will cost over R100 000.
The 40D on the other hand can produce good pics with lower spec lenses cos it has a smaller sensor - so the whole system costs a lot less.
My suggestion is to buy the 40D, then buy good lenses as you can afford them, then move full frame.
Why 5D.....well you have heard all the technical stuff which has been eloquently stated by others.....but in reality somehow the 5D has hit a sweet spot for glamour type photography. It is not a sport/action/wildlife/press/action camera and if that is your field there are better options.....but in the studio photographing a model....I still defy anyone to prove to be that there is a superior camera in the 35mm type format. There may be cameras as good on paper but as BC Image said "will they produce a better pic?" - I doubt it. It has something to do with the number/size and sensitivity of the pixels, and I am not adamant as to what it is, but I know it exists. I am very worried that the 5D Mk11 may loose this as it will be 16.9MP on the same size sensor with 14 bit technology - so the jury is out.