<blockquote><hr>
Isent it time to change armor again so there is pro and con to use leather and plate?
What should be the difference and why?
[/ QUOTE ]
If you are comparing runic items, it is clear that leather is better than plate in most cases due to the fact that the former is med, thus giving the wearer a superior advantage (if he has invested in the med skill).
However, plate armour are not necessarily inferior to leather. The jackal's collar is one of the most useful warrior's gorget out there... and it is plate armour. I also see some warriors wearing the helm of insight (plate helm).
Warriors who choose to wear non-med armour also have a wider variety of armour to choose from. One of my warrior prefers the gauntlets of nobility instead of stormgrip because the resists fit nicely. Of course, he happens to wear the jackal's collar also to take full advantage of the dex boost.
I am not actually opposing your proposed change. However, in considering whether to either nerf leather armour or boost plate armour (or other forms of non-med armour), we need to know the benefits of both leather and plate.