old Canon 50 1.8 vs. new version (MII)

[RGB000111]

Before acquiring my EOS 10d I used an old EOS film camera model that came with a Canon 50 1.8 lens. Is there a great difference between the old build and the new version of the lens?

[Jesper]

I don't have either of them, but the main difference seems to be that the old version is better built - it has a metal lens mount, while the mount of the new version is plastic. Optically they're supposed to be the same. If you have the old version, there's no reason at all to buy a new one.