You can tell it's Eustace because they gave him weird boots with an Ugg-like texture. If it were indeed Peter, he'd have a cooler costume than Ed's clearly visible boss leather boots. Remember in PC when the battle just starting? They have this great shot of Peter and Edmund under a stone arch; Peter is in full armor with badass greaves strapped over sollerets. Edmund is dressed almost the same, with significant differences in tunic cut and fabric, less armor compensated by more leather, and the most standout gross level of ugly, tan suede boots. The may have even had fringes. And then they made him use the lame crossbow on horseback for a whole sequence. They make up for it though, with that awesome moment of Ed tossing the bow away and taking out his swords. BADASS and FABULOUS. Er... what was I talking about?

Right. Because the films looooove to emphasize that Peter outranks Ed in bossness, almost to the point of dissing Edmund via subtle costume details. This carries over, I'm guessing, into VDT with Edmund looking cooler than Eustace. Thus the Uggs of Eustace.

I suppose the this the place to say that I loathe Ugg boots and suede in general, and love leather. And Edmund.