Where Nani averages an assist every 2.9 games, Valencia is a much more efficient provider at an assist every 1.9 games.
Valencia's selfless play has seen him make more passes than Nani per game, and even at a better success rate, 86 percent pass completion to Nani's 80 percent.
In terms of ball retention, Valencia comes out on top as well. On average, Nani gets dispossessed 2.4 times per game, whereas Valencia gets dispossessed a mere 0.9 times a game.
Furthermore, during the 2011/2012 season were both players played almost equal amount of minutes (2100ish):
Valencia put in 68 tackles, whereas Nani had 38, to a 6% better tackle success ratio despite having put in a staggering 80% excess amount of tackles.
Add to that, the minutes in between Valencia's tackles (30) was half of Nani's (56) while completing more interceptions, clearly indicating a higher work rate, or at least a more efficient one.
Valencia also made 12% more passes to a 10% better completion rate, potentially suggesting he contributes more or better to play than Nani. In addition, cross completion was marginally better with 3%.
Lastly, as for shots, Nani made a lot more attempts. However, he only hit the target 39% of the times, whereas Valencia hit it 47% of the times. Add to that, Valencia's chance conversion was significantly better at 24% to Nani's 16%.
Now tell me, how was Nani better again? The case for consistency versus unpredictability is obsolete these days, that moment of magic Nani supposedly produces doesn't come around nowhere near enough to justify the preference for his 'guile' over Valencia's evident efficiency. Manchester United is a collection of team players, facts speaks for themselves, Valencia is the better team player.