t34/85 has 120 penetration, 40 range, 2.5 AOE, 124 front armor, 800 hp, and it shoots every 6.25 seconds.
su85 has 170 pen, 60 range, 1 AOE, 180 front armor, 640 hp and shoots every 4.25 seconds.
both do 160 damage.
the t34/85 is the better all around tank obviously, but still cant compare to the su85 for AT. with good micro, you may be able to kill at panther with 2 t34/85s, especially if you ram with one. overall, id say they would lose more often than they win though unless you can hit the panthers rear armor.
