
It's not just Light you upgrade on Armour... (Destiny)
FWC Astrolord Grips. Fully Upgraded on the left, fresh from the store on the right. Ends up with 5 more Intellect and 4 more Discipline after the upgades, in addition to the obvious Defense and Light level increases.
Hadn't seen anyone point this out yet so I thought I would. This makes it more difficult to compare your existing armour with new pieces you acquire: is a new piece worse in absolute terms, or just because you haven't upgraded it yet?
It doesn't make as much of a difference as Light, but it will help you get your Grenade/Super/Power Melee back slightly quicker. Up to several seconds quicker for the Super if you upgrade all your armour pieces.