My choice would be robe.
Besides looking better, robes boosts your healing power as well. Since you're a main bard, you dont benefit from the light armor passive ( as you're not using cleric rod as main weapon ). Also, with the combination of robe + mana tambour, you have more chance of surviving a wizard stealth nuking you.
BTW bard main in PVP is sexy

A bit like a batter between music and brute force
