First, there are NO current versions of the old 150-500mm Sigma, and there was only one version of it when it was a current lens.
Second, have you not read the specs between the Contemporary and Sport versions of the 150-600mm lenses? Apparently not.

Feature,...…..Sport ,...………………………………..Contemporary

Weight,...…...100.9 oz,........................…...68 oz
Dims.,...……...4.8" x 11.4",..................…….4.1" x 10.2"
Const.,...……..24 elmnts, 16 groups,...……...20 elmnts, 14 groups
Sealing,...…...Fully weather sealed,............None
Barrel,...……..100% Magnesium,.........……...100% Polycarbonate
Hood,...……….Magnesium,..................……...Polycarbonate

Seems I can find many differences looking at the specs that you seem unable to read. I wonder why this may be????