Both are flukes, but as much as it pains me to say, Mandy. Del Shitro beat Nadal who couldn't serve and Noserer who choked in the most pathetic manner.
Mandy despite being helped by his weather manipulation magic, USTA and many other factors, actually beat exhausted No2e to grab his title. Plus previous achievements must be taken into account as well: Del Shitro can't even win a masters title, while Mandy has a few masters titles under his belt as well as several slam finals.
All in all, Mandy is more deserving slam champ IMO. Del Mugtro is a brainless ballbashing mug who fluked his slam like Johannson, while Mandy, despite lacking game tried his best time and time again until the stars aligned for him.
And didn't Del Potro actuall beat Nadal and Federer
? He didn't even ned any 'weather manipulation magic' or 'USTA' for it.
Who did Murray beat before the finals? Lopez, a guy with one shot. Raonic? A guy with one shot, Cilic (choked but should have been up 2-0), Verdasco (a choker but was unlucky with some calls). Even in the final Djokovic wasn't great and the windy conditions made him play even worse. I'd take JMDP by a clear shot. I understand Nadal fans always like to play the injury card but it's not like Nadal is some hard court GOAT who can't lose when playing well and beating Federer is clearly more impressive than beating Djokovic at the US Open.
Murray didn't face Verdasco in the US Open.