Royster is the guy I know was on their radar leading up to the draft. I don't know if Helu was as well or if they were surprised to get him.
My guess is Helu has the advantage, based on what I've heard so far (and what I'm sure everyone else has too). But it does seem that we're dismissing Royster awfully quickly. And I suspect that has as much to do with the fact he's a Penn State RB than anything else.
In the meantime, read more hatterade from the media on the Redskins (particularly Roy Helu)
NFL.com news: Under-the-radar rookies poised to impress during preseason