Both arms, but not too much shorter than the right hand one.

And now you've pointed it out the black part of the armour would look good if it was inflated slightly, it'd create more shadows when it comes to rendering and make it look more real.
(Because I do see eyeballs in armour walking down the street swinging swords everyday...)

Still, overall it's looking good, I really like the style of your work, it's instantly recognizable as yours for one, and always seems to have a good sense of fun about it.