Since I assume neither of you participated in Tuetens/Gnjus tournament that didn't have any restrictions what-so-ever, I can guarrantee you that the team(s) that went full plate failed miserably against team with lighter equipment.
Why? Because you cannot keep up in group fights. In 1v1 I agree it gives you a significant boost, but not in matches/group fights.
Really? Then what is keeping people from going full loomed tincan? As archer you have almost no chance against that!
Really? I disagree. Easy headshots, friend.