Part of the problem is that the information at the
main r3mix site is notoriously out of date. Other than making sure the forum remains up and running, the owner of that site has not been active in maintaining or updating it for quite some time. For example, the
c't magazin listening test that was cited in an earlier thread on the MJ forum as recommending --r3mix for use with Lame was done in February 2000.
"In february 2000 c't magazin organised a blind listening test. 300 Audiophiles were involved, finalists tested 17 1-min clips from different artists (classic and pop):"
I'm not an expert on the Lame development timeline, but I don't think the --alt-presets even existed then, so at that point in time, with that version of Lame, --r3mix was probably the best setting to use. Of course, in the 2 1/2 years since the aforementioned test took place, the Lame code has certainly gone through numerous revisions and updates and the --alt-presets are designed to take advantage of code-level features in the current version of the encoder that are not accessible using the normal Lame command line switches, which is all --r3mix uses.
So, if you really want the most current information and recommendations on what settings should be used with the current version of Lame, check out the
r3mix forums and
Hydrogen Audio forums.