They were both legitimate, but Del Potro obviously had the tougher road
. I'm not saying Berdych and Djokovic aren't great players, but Federer and Nadal both in their prime years
are arguably the biggest iron wall to the Grand Slam gates there has ever been.
I agree with both points that Federer and Nadal are an iron wall in grand slams in their prime years and that both titles are legitimate however I disagree as to who had a more difficult road. In 2009, neither Federer nor Nadal were in their prime. Federer's prime years were 2004 - 2007. Nadal was injured for a couple of months. According to win percentages, 2009 was Federer's 6th best season. It was Nadal's equal 5th best.
Yes, Federer is a tough customer on fast hardcourts. But, Nadal on fast hardcourts during his tendinitis season after already having lost in lead up tournaments in Canada and Cincinnati? It was a greater feat for Murray the previous year when he beat a younger, healthy and ranked #1 Nadal.
Presently, Murray is in Roddick territory with more M1000 titles and more majors finals. Del Potro is in Thomas Johansson territory but with less M1000 titles.