I have been trying to understand the differences in the new 1Ds vs the new 1D beside price and megalpixel. Why do people choose one over another? Especially if price was not a factor.

Thanks
shane

Speed. the 1Ds is 5fsp, the new 1D is 10fps. Not sure what the other differences are (other than resolution), but that is the one that sticks out the most to me.

The 1Ds MkIII is geared toward high end fasion photos. The 1D MkIII is geared towards pro sports and action shooters.

Speed, File Size, buffer size, intended use.

A 1.3x crop factor body gives a tighter field of view with the same lenses- often useful for sports. More useful however is the fact that despite using the exact same AF array, a consequence of the smaller format is that the AF ellipse covers a significantly larger portion of the frame allowing better AF tracking of subjects dynamically moving within the frame itself.

Meanwhile the 1.0x 1Ds Mark III offers a few refinements overall, but the big differences are burst depth (1D Mark III has a larger buffer capacity, though it fills faster), viewfinder size/brightness (1Ds mark III viewfinder is supposed to be a dream come true, though the 1D3 is no slouch), continuous shooting rate (5fps on the 1Ds Mark III is crippling for some sports and action photographers, while many will use one in conjunction with the 1D Mark III when speed isn't their #1 concern), resolution (21mp vs 10mp in RAW/L, 5.7 vs 2.5MP in sRAW), and of course high ISO performance (1D Mark III has a big edge here, hence it allowing up to ISO 6400 vs 3200 for the 1Ds mark III in ISO H).

the 1ds is aimed more towards nature/wildlife photographers, while the 1d aimed at action/sports photographers.