Tange Prestige is heat treated for more strength after lightening further.
Like 753.
Just compared my 93 Giant in Tange Prestige and a full 531 Holdsworth. The 531 feels about the same weight when lifting the bike but feels 'lighter' and more lively when ridden. It's a totally subjective thing though, they are both great bikes. Tange 1 and Tange 2 are definitely heavier.