Which is more likely to yield better overall low-light performance, Canon 1DS2 or 1DIII?

Question

1DSII is full-frame, meaning I can at least theoretically get a little more performance via slower shutter speeds without shake (using 1/f general rule of thumb). But the ISO limit is 3200 (H). Also I already have a 1DII and am familiar with its (somewhat peculiar) button-pressing scheme...plus the 1DII and 1DSII use the same batteries.

On the other hand: 1DIII is APS-H (1.3x crop), ISO max is 6400. Plus it has newer DIGIC processors. But I know there was some concern about auto-focusing of the 1DIII (maybe very specific conditions?).

My use will be widely varied, but a big portion of what I do is dance photography (on-stage, with poor lighting) and it's one place where the camera/gear really does matter.

It's not too hard to find either of these bodies used, and the price is comparable. Which one is likely to serve me better?

Answer

When looking into camera gears I don't own, I use DxOMark to get an idea of perform and quality of certain aspect.

• DxOMark Side by Side Comparison of Canon 1D mk3 and 1Ds mk2

According to DxOMark, 1D mk3 able to produce "lower noise high ISO" image at up to 1078 ISO while 1Ds mk2 is at up to 1480 ISO, roughly 0.3 stop better.

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