The 1DsII is an amazing machine, with not only all the resolution you'd expect from a 17 mp camera, but very good dynamic range (I'd say about an extra stop compared to a range of other Canon and Nikon DSLRs I've used). Note that my comparison cameras do NOT include any of the Fuji SuperCCD models, nor the 5D. With the autofocus problems the 1D III has had (I'd assume the 1DsIII will either have similar issues, or be delayed), I'm all the happier with my 1DsII (which I bought this April). The 1DsII can print 20x30 easily, in a fine-art landscape application (so more than that doing anything less detail intensive).
There are three problems with the 1DsII... It's big, it's heavy, and it's expensive. There's no denying that it is all three of these things, or that the 5d is not as bad in any of those respects. On the other hand, the 5D is nowhere near as well built as the 1DsII. The 1DsII is the best-built camera out there (along with the other 1 series Canons and possibly the pro Nikons), which I would imagine is important for someone working in Antarctica. In a harsh environment, I'd take a 1DsII over a 5D in a millisecond. The only caveat in a very cold place is the NiMH battery pack, which is less optimal than a lithium ion pack in the cold (get an extra and store it inside your clothes).
Unless there is something specific you want that the 1DsII doesn't offer, I recommend it highly, not least because it's an incredibly well-proven camera that won't have any new-camera teething troubles. On the other hand, you might want to wait until right before you leave (give yourself time to test it before you go), to see if the 1DsIII will come out and drive the price of the II down.
I completely agree - but DR and sharpness seems to depend a lot on what RAW converter used. I have just been playing with The new ACR and while functionality is great and speed something else, disappointingly it smears fine detail , clips highlights ( no matter how I adjust the sliders ) and doesn't deliver the lovely colour and detail from the 1ds2 that seems to come straight out of C1 pro or LE for me ( I leave the sharpness and noise reduction alone there - ironically its better to do any of that in photoshop) - a lot slower way of working but the results are superb. I find most of the same issues with the Canon software as ACR.
While I don' t own the 5D( but do own the 1ds2) , I have done a few comparisons and find the two to be almost indistinguishable as far as file quality is concerned, with the 1ds2 resolving a little more detail but only with the best prime lenses and solidly locked off on a tripod( for the most part I see little real advantage gained in the extra few MP) The 5D may or may not have a little more DR but it wouldn't be surprising given the slightly larger pixel size.
I do have a Imacon 132c to compare and also have found Moire in fabric and landscape - and then the flexcolour noise reduction seems to take care of ninety five percent of it.
The colour depth and tonal range of 16 bit capture ( not to mention the sharpness due to lack of AA filter) exceed the 1ds2 - by a considerable margin, particularly in shadow detail. But the flexibility and speed of the 1ds2 compared to MF is another issue entirely.