The main reason some LDs sound better is that the surround mix was done purely to be a surround mix.

When DVD came along one of the priorities was that if the doofus that bought the DVD only had TV speakers or a mono or stereo setup and chose the surround track to listen to, that the dialogue would still be intelligible and the sound would still be okay. This led to many DVD soundtracks having severely compromised 5.1 mixes compared to the LD mix which was only ever designed to sound great in 5.1

Heat was one of the titles that really suffered in DVD vs LD.

Now BD sound quality craps all over laserdisc from a technical standpoint, but LD can sometimes have a better mix, especially on films that came out before they started doing 7.1 etc.