[Pedro Paulo Gaião]

So, since I have been looking over modern reconstructions of historical full plate armor (see here) I eventually noticed that, although closed/full rerebraces were around Europe since 14th century, there are plenty of 15th c. historical and reconstructed armors with rerebraces protecting only the outer side of the arm, while the inner side (which touches the torso) was left exposed for mail protection (at least I believe all full harness were to be covered in mail at exposed areas; like here). Considering both styles were contemporary, what explain their difference? I did some assumptions:

1) cultural preferences; like local tastes or climate
2) workshops exports having their own style
3) cheaper alternative for non-gentle men-at-arms

What do you think?