The sword is larger because it is intended to be used mostly from horseback, thus longer for reach and perhaps also a bit heavier for blow, not sure about the latter one.
I used to have two Rohirric swords as dual wielding champion, but I dropped it for the nice Anorien swords, it looked a bit silly. In regards to cosmetics in Rohan you are absolutely right, i have still to test out more of the Wildermore recipes, but a lot of the barter items are very good looking.