I also find that sandpaper gives a more glossy finish than whetstones of equivalent grit,maybe is the way the steel stays on the paper (burnishing?) rather than exposing fresh grit on a stone,or the grit rating on EU(ISO/FEPA) or E.U.A (ANSI/CAMI) is different to JIS....
There may indeed be differences in standards. I prefer the feeling of sharpening with a whetstone, but it is a difficult problem because it is hard to make many whetstones to match the R.