This is why this game is so frustrating as compared to say the Elder Scrolls series where all of the algorithms for determining results are well documented and you can calculate exactly what the impact of changing a weapon or armour or spell is.

But that is just the OCD numbers geek in me - as the great pen and paper game designer Greg Stafford says 'x (x being whatever fictional or historical people the game represents) don't know the numbers'.

Having an element of mystery is in its way more realistic - Oda Nobunaga didn't know what the precise impact of increasing his ashigaru's armour or lengthening their spears was - he just knew that more is usually better.