The usual "skill is what matters" and "the camera is only a tool" rhetoric is true, ... BUT ... the better the tool, the better the results all other things being equal. I did not have a 1Ds MkII, but I did use the original 1Ds for a few years. It IS big and heavy and high ISO performance is poor. My 1Ds looked bad at 800 and practically unusable at ISO 1200. The MkII goes a bit higher in ISO, but it still does not give much better results.
A HUGE problem with those early digital 1D series of cameras is user interface. The cameras are a pain in the rear to actually use. It is as if a drunk madman designed the things. It takes dancing with two separate button pushes to change things. It is NOT user friendly AT ALL. You will have to stay in constant practice with it or you would be lost trying to use it only as an occasional back up camera.
I have had two 5D MkII cameras and currently have the 5DSR. There is no comparison between the 5D MkII and a 1Ds MkII. Image quality, especially at high ISO is much better with the 5D. The 5D has a sensible user interface and it a smaller and lighter form factor. The small battery in the 5D lasts as long as the huge, heavy thing in the old 1Ds bodies.
I HIGHLY suggest you save more money or whatever you have to do to get the 5 series of camera instead of the 1Ds series.
Actually, you would be better off to spend some more and get the 5D MkIII. It has a far more robust focus system than does the MkII and even better high ISO performance.
But between the 1Ds MkII and the 5D MkII, there is no question, go for the 5D MkII.