This sounds like a job for Devil's Advocate Man!
If we consider them nearly equal on finishing ability - with Van Persie's superior total offset by a higher amount of games played - we can really only make a difference between them in terms of what they contribute to the team. Now, work rate is subjective, but all those who say Rooney works harder than Van Persie have a point. However, I reckon he seems to be slowing down, and working much less hard than he used to. Moreover, he's a 'hole' player nowadays: part of his JOB is to prevent the opposition regista from controlling the game. We don't know if Van Persie would work as hard as Rooney as a trequartista, but if we take one isolated example - the 1-0 City win at the Etihad, where Rooney was a lone striker - when the roles were reversed, Rooney didn't seem the be exactly buzzing with energy. That's not necessarily his fault, more the fact that as a lone striker, there's not much to work hard FOR.
As such, with work rate a dodgy and subjective system to be basing our analysis on, we have to use stats to decide on the key question here: Is Rooney really that much more 'complete'? Apparently he offers more to the team than just goalscoring which Van Persie doesn't, or perhaps does, but to a lesser extent. But the facts and figures seem to say otherwise: not only does Van Persie have more than double Rooney's assists (in a team that scored fewer than United, let us not forget), he also has 92 key passes to Rooney's 51, indicating that creatively at least there's a strong argument for him being a more complete and thus better player. As one final clincher, consider the fact that Van Persie has not only doubled Rooney's assists and nearly doubled his key passes in a team with fewer goals scored, but has done it in nearly half the amount of average passes per game. If we're going on team contribution stats, there's only one winner, and it's the Dutchman.