All 8 bit formats are roughly the same quality as long as they are lossless. If you plan on going out to Digibeta any 8 bit format should be fine. If you plan on fliming out I'd go with a 10 or 16bit format for the extra color detail. Such as Cineon, DPX, or Tiff 16.
Also, when you say keying. Do you mean key-frames for your animation or do you mean color keying your stop motion animation to composite it against a different background?
For doing keyframes. Any will work. For color keys I'd use a higher bit-depth format.