So again compound bow vs plate what do you guys think?
Do you mean, modern compound bows with cams?
Well, I only shot once those in my life, and even though I âalwaysâ had, hm, letâs say historical bows, I admit I found them freakingly awesome. About their capability, on the other hand, I am not sure. I read some hunters who use bows state that such a thing with a hunting arrowhead can go (edit: shoot. It would look silly if the hunters would throw the bow through the poor animalâŚ) through a deer or break the spine of a wild boar, but I am sceptical as long as I see some valid proof.
Therefore I could give a better judgement about historical bows, but just to be safe, I wouldnât stand in front of such a thing in a cuirass. 
By the way, these questions could be maybe partially answered by the help of finite element analysis softwares. Years ago I COUGH-COUGH bought ANSYS, but I never really got around to actually learn how to use it, even though it could get handy - still, I remember perfectly good that it had a simulation of of a modern bullet (lead with steel jacket) penetrating and deforming a - probably - steel plate.
Many variables canât be modeled too well in terms of foreshadowing, of course, like the inhomogenities of the wooden shaft, the non-perfect arrival of the arrow, the non-perfect axis of the arrow shaft, the properties of the historical steel plate material and whatnot; so testing IRL would be still pretty much preferable. The good thing about FEM would be on the other hand that it would be
- repeatable in terms of total control over the parameters and
- the ability to change every parameter differently and in arbitrary resolution.
Apart for the exact question, I seriously think that neither âsideâ (The [generic historical bow] penetrated the [generic historical armor] / it did not) is absolutely right. The average thing that happened was probably âaround inbetween.â People wouldnât use armors, it it were ineffective, and so is the thing with bows.
So, probably a pack of guys charged some archers. The archers shot a volley. Most of the arrows fell to the ground without harming anyone, some of them got catched by shields, a few of them bounced off of the armors and a few of them hit some guys in the arm, or in the foot. They scream, call an ambulance, the rest go on, another volley, oops, some guy got hit in the neck, bad luck, an other guy got an arrow in the chestplate, it stuck in there, but the armor and the gambeson in the end prevented any kind of serious damage to the wearer. Two of the guys now cover behind their shields and watch in shock the third guy bleeding out of his neck.
Et cetera.
In a way, it is kind of similar question to the good olâ âlongsword versus katana.â Reality is usually complex, unpredictable and dirty, but often restrains himself from the clean extremities.
