I am guessing you are asking whether the Training trait affects XP in PvP. Yes, it should affect how much XP you gain from kills in PvP. But it's not that much and it does not affect XP from other sources like quests, Battleground match rewards or keep capture/defense rewards.
Generally using training gear in PvP just means others will have an easier time to beat you up, so unless you know what you are doing and trying to make it harder for yourself, I would advise against using the training trait for PvP. But if you have some nice crafted set item that happens to be Training, then you should probably keep it over using a nonset item that has a better trait.