What is there difference between the one disc and two disc versions aside from special features? Are the transfers the same or is the one disc version worse quality? I think I heard the one disc is non-anamorphic, but I'm not sure, is that true? Thanks.

The old disc is non-anamorphic, and has 2.0 audio only, and pretty much no extras.

Well that settles that. Haha, thanks!

The version I rented was a double-sided (full screen/16:9 anamorphic) but also single-layer.

The two disc version might have a higher bit-rate & better quality on a dual-layer disc.