half the price
almost half the weight 565g vs 915g
shorter 88mm vs 117mm
not as sharp or as optically corrected but nevertheless this is a very sharp lens even wide open (comparable sharp to Canon EF 100mm L but not as sharp as a Zeiss 100mm)
can use tele-extenders whereas apparently the new one can't
uses 58mm filters instead of 77mm
close focus 0.5m instead of 0.39m
different optical design with almost half the number of elements and groups
no extra coatings
8 blades not 9 blades
aperture to f/32 not f/45 but then sharpness at f/32 is already less than half while at f/45 it falls to a quarter of maximum sharpness
arguably nicer, less busy bokeh