You can't go wrong with either piece as an upgrade. It's difficult to make a reccomendation without an actual armory of you to see where you need stats more.
I'm assuming you are the Gigga in Damage Incorporated on Feathermoon. I would get the [item]sunguard legplates[/item] first. I think it would be the biggest upgrade for you and will get that big 100 badge purchase out of the way. The fact that it looks awesome with the chest is a nice little bonus too.