Type 90

Overall more firepower (the shells are heavier so they actually deal more damage than Type 3 despite less HE damage)
Also the shells are so heavy they go through most (if not all) armor setup when fired at max angle.

the Type 90 also has a higher rate of fire (shorter reload).

the downsides are a slight loss of range (but to be honest this is so small it's almost not noticeable) and the guns are slightly heavier (actually the guns are lighter but this is deceiving, since the ammo binds are a lot heavier so total weight fully armed is more)