All About Eve (1950)

The 1988 CBS/FOX LaserDisc sounds very very bad, having apparently been sourced from much higher generation elements. 

Between the Fox DVD from 2003 and the two blu-rays, I'd probably take the DVD, which has the most natural sounding dialogue and less noise reduction than the blu-rays. But they're all very similar in the end and sound rather stifled.

I'd like to hear the later (1996) Fox LaserDisc.

All About Eve (1950)

This one is peculiar. The 5.1 as a mix is quite mediocre and is certainly just a (phasey) rechanneling of the mono. But, the high-end of the mono mix included on the US blu-ray has been further attenuated, while the 5.1 hasn’t undergone as much neutering. I’d still take the mono, but it could certainly sound better. The mono is available on both the US/European blu-rays.