At first, I would have said Federer had it easier. Although New Balls was a really strong generation, Federer didn't have an ATG in his generation, while Nadal and Djokovic had each other. But the Big 3 ended up having a really long career, unthinkable years ago, and Federer ended up competing for a decade with two ATG who were five and six years younger, thus having an age disadvantage. OTOH, Nadal and Djokovic didn't have any ATG coming up after them so they could continue racking up slams comfortably in their late-'20s and early/mid-'30s. Maybe I'd say Federer had it tougher, then Djokovic, then Nadal. But there really isn't a strong difference between them to suggest it's a relevant aspect to mention. For instance, Hewitt had a far easier competition than most of the slam winners that came after him. That's why he could get far more weeks at #1 than Murray who is a more accomplished player, or than Wawrinka, who couldn't even get to #2. But in the case of the Big 3, I don't think competition is a relevant aspect. They all had some very tough draws and some draws that were a joke.