Isnt Erryck and Arryck a myth from King Arthur,
I think King Arthur is fighting a war against the saxen thus preventing him to find for the hand of his wife himself. He sends his best swordsman instead, this swordsman must fight the queens father chosen champion. (his father is against the match), he chooses Arrick (one twin), and the duel commences, trickery is into play though and when a pause commence the other twin changes place (Errick) with Arrick since he himself is too tired to continue.
However this trickery has no affect, and the duel soon ends with the swordsman winning the queen (guinevere) since Errick is not the swordsman arrick is (or vice versa). Now i amnot sure of what i typed is acurate, but perhaps boaz can make a theory of it, it is his hobby after all.
Also faceless,Jon is quicker then Robb so the comparison doesnt hold.
if you compare Jon and Robb without giving them attributes, i'd say Jon wins, just for the comment he made about Catelyn looking sour and i think he also said that he usually was a tad better.