A newcomers q about 1ds, MK11(fixed), MK111

I have a used Canon 1ds and the dirty sensor is taking its toll on my patience (I know I can send it in) and even more the bad picture quality when using only relatively high ISO speeds. (the quality at ISO 100 though is to me far better than film)
I can afford a d MK111 but not a ds MK111. I could also afford a used ds MK11.
Can someone tell me the difference in picture quality between the 1 ds and the
d MK111 and the difference in picture quality between the d MK111 and the ds MK11?
Is it so that when using the smaller sensor the quality is (partly) making up for a full frame sensor since the smaller sensor uses the sharp centre of the lens?
I like bird photography and wonder if I would have much use for 10 frames per second compared to 5?
I am new to this forum and technologically no genius, so please bear with me.

Liu

If you shoot birds, the 10FPS will be a huge bonus. 3FPS is just enough to get Eagles flapping and catch the wings in the down position every time. 5FPS is better and 10FPS you would catch shots of the bird in positions you normally would never see otherwise. Even your eye might not see half of what 10FPS will catch for you. All assuming you have the light to shoot that fast.

You also want the crop factor. The bigger the better. This will cut down on the cropping you would have to do in post processing. I only have the old 1D, and know nothing about the newer models, but have read that the 1DsMk2 is not really suited to birds, but more for the studio, as it takes too long for the camera to write to the card. Tenths of a second will matter when shooting birds, especially at higher frame rates.

Hope this helps.

If I had the money, I would buy a 1DMk2N for birds. Spend the rest on glass.

Welcome to POTN! Did you try to clean the sensor yourself? It really isn't that bad once you learn how to do it yourself.