has good info, as does http://en.wikipedia.org/wiki/Canon_EOS-1v
(the timeline down the bottom).
From top to bottom, a few differentiators of quality:
1V, top of the line. 45pt AF (same as 1D/s), 21-zone metering, spot-linked metering, interchangeable focus screens (same as 1D/s), 100% view pentaprism, built like a tank and weather sealed (as well as any 1D/1Ds), 3fps or 10fps with motor drive, doesn't fog IR film.
Older 'top', the 1NRS. 5pt AF, 10fps with power drive, 100% pentaprism, 16-zone metering.
1-rung down, EOS 3. Same 45pt AF (but with eye-control), same screens, 97% view prism, pretty much all the same as 1V, but does 4fps or only 7 with motor drive, and the film counter does fog IR film.
Older 'next top', EOS 5. 5pt AF (with eye control), 94% pentaprism, not as well sealed as the 3 (afaik). inbuilt flash (the 3 and 1V had no flash, like the 1D/5D).
1-rung down, EOS 30V. Only 7-zone AF (with eye control), first camera with E-TTL II flash metering, 35-zone metering (it was a lot newer than the 3 and 1v), only 90/92% viewfinder coverage.
1-rung down, EOS 300X. 7-pt AF, 90% view pentamirror, 35 zone metering.
...everyone knows that once a new camera is released, the previous model is rendered useless and unable to produce usable images.
That's why I bought an EOS 3. It's only as good as the Velvia 50, Efke 25, and BW400CN that I put in it...