I own a 5D mark II and I do event photography. I have numbers of lenses in my collection and that's the reason I am looking for a second body, because changing lenses in event is a real pain. Do you think a 5D will be good as a second body beside 5D mark II? Or do you suggest a crop body?
What are you looking for in your second body?
- Backup in case first body fails?
- Ability to use two cameras a once; One with a 135 f/2 one with a 50 f/1.4?
- Ability to use same lens on different camera but get a different look?
- Ability to use same lens on different camera but get the same look?
You need and choice of a 2nd body may change depending on your answers. I think a 5D would be a great 2nd body, but so would a 7D or maybe even the cheapest available Canon (in your case) SLR.
With the advent of the 5D mkIII and the subsequent price reduction on the mkII, I think I would be buying a 5D mkII instead. The biggest reason would be comparable output, though if you had the money, a mkIII and mkII combo would be better. Net effect, the original 5D is simply passed by and I wouldn't consider it.
As an aside, I made a similar decision with the Pentax K-5. At first I was dual shooting with the K-5 and K20D, but the limitations in the K20D became way too obvious and I sold it off and bought a second K-5 instead. My sense is that you'll run into the same basic issue with the 5D options, so don't spend the money, you won't recover it.