For a start, I absolutely love the 1Ds MKI and I have NEVER shot with a 5D, so take the rest of this post with a pinch of salt! But considering you're not worried about high ISO performance, I would recommend the 1Ds almost immediately.
I think this is a thread that could potentially go on and on forever and there will be no conclusions to be drawn about it. Image quality is very subjective. If you do a search at this forum for a thread titled '1Ds MKI users unite' or something along those lines, it should bring up some sample photos. There's been multiple other threads discussing the 1Ds MKI vs the 5D MKI.
In each of these threads it's virtually a tie. Even if we took the simplistic method of tallying up votes for each camera and choosing the one with the most votes, we could be off the course because for sure, there are heaps more 5D users than 1Ds users. We need to bear in mind that the 1Ds is a number of years older than the 5d and back in its heyday retailed for an absolute fortune, and only the pros or the very rich could have it. Considering it is still frequently compared to the 5D should be at least a hint of positivity about the 1Ds.
The other simplistic method of evaluating these two cameras in a more objective fashion is to visit the DXOMark website. The 5D obviously scores higher than the 1Ds in all regards when you look at the plain 'Overview' screen.
Hence, in an objective measurement, you're better off with the 5D if you want to follow the numbers. Ultimately though, its the subjective qualities of the 1Ds that might win you over. Believe it or not, two co-owners of a rental equipment company in my hometown have offered to buy my 1Ds, citing the 'arty' or 'DIGIC I' color as being attractive. These same guys have access to everything up to a 5D MKII in their stable. Personally I enjoy the appearance of the grain in the 1Ds images. Plastic-smooth is not my thing, and neither do I like the watercolor-like noise blotches I see from some of the newer cameras. I'm afraid to say that you do need to shoot with both to see what you like.
I landed with the 1Ds not by choice actually, but by circumstance because I got it cheap from someone who, by chance, wanted my 1D MKI badly, and just as badly wanted to rid himself of the 1Ds. Interestingly I found him posting a 'Want to Buy' for a 1Ds a year and a half down the track. Think of that what you will. But after sticking with the 1Ds for close to 3 years now, I absolutely love it to bits.