[Edi]

Scale mail is better because when well made, it provides equal protection for less weight than chain mail and actually better protection against bludgeoning weapons. Chain mail can actually exacerbate bludgeoning injuries with the links driven into flesh and worsening the damage.

Secondly, scale mail provides far better weight distribution, meaning it is less cumbersome for the same weight and easier to move in. Some stat adjustment would indeed be in order.

It is also a historical fact that plate armors were less cumbersome than chain mail, since they also provide the same better weight distribution and are no halfway as cumbersome as most role playing game systems, especially D&D, would lead you to believe. Unless of course we're talking about tournament plate, which is a chapter in and of itself, far heavier and primarily intended to prevent accidental fatalities. It was never used on the battlefield due to the incredible weight.