Little Mermaid and Aladdin were orignaly Dolby stereo. Everything since then is an upmix.

I do know the Little Mermaid had a surround up/re-mix for the theatrical re-release and that track was included on the first DVD. After that you start getting Disney’s crap home theater mixes instead.
I’m not sure about the history of Aladdin, I’d assume it’s identical since the 35mm transfer is also a 5.1 DTS track.

Most of the audio coming from the from would be the most accurate.

Btw, I’ve seen the 35mm audio track of Aladdin, but where I found it they don’t have it synced to any video because of site rules (or something). You may have to sync the track yourself, but it’s worth it since there were lyric and dialog changes. Little Mermaid, afaik, doesn’t suffer from that.