Is 5D AF better than 20D's? (was: 20D, 5D or 1DMkII for dance and theater?)

The 1D Mk2n has 45 AF points, the 5D has 9. Look, if you have not done so yet just get your hands on both and then tell us what you think. Will you ever want to change focusing screens? The 1D gives you 10 interchangeable ones to choose from, the 5D just 1. Do you plan to keep and use it for a long time? The 1D will be just broken in good when the 5D poops out.

the 5D has 15 focus points, not 9. 9 are selectable, 6 are "expansion" points used for servo mode. And the 5D has 3 Canon focus screens available, and two (expensive for now) aftermarket screens available. They can be changed as easily as on the 1-series. The 5D's shutter is rated at 100,000 operations, the 1D2 at 200,000 - both pretty substantial figures.

I agree though, it's best to get your hands on both and compare in the types of situations that you intend to shoot. I did.

I stand corrected, Canon's web site says "9 AF points (plus 6 invisible Supplemental AF points)" for the 5D. However, unlike the 1D and 1Ds, it makes no mention of interchangeable screens for the 5D, neither are any listed under accessories for the 5D as they are for the 1D series.

Well, I have one of the focus screens besides the original. There are 3, including the original, the Ee-S high-precision, and the Ee-D grid-type. What's missing so far is what might be called the Ee-B with a microprism center, though Brightscreen is offering something like that for a rather steep price.

The invisible focus points are only used in A1 Servo mode, and A1 Focus mode when the camera goes into tracking predictive focusing. In single shot mode, they aren't active.