Becker, in a column for the Daily Mail, rated them almost the same level across several categories.
Both Federer and Nadal count their forehand as their greatest weapon from the back of the court, but the six-time Grand Slam champion finds Nadal's more imposing these days.
"Federer’s shot is a bit of a throwback to the eighties, a flatter stroke than Rafa's," said Becker. “Devastating from anywhere on the court, but not quite the monster that the Spaniard possesses."
Nadal's forehand is notable for its high follow-through, he added, saying, "That is what gives it so much power and spin, making it bounce up high in a way that has, in particular, broken down so many opposing backhands."
Becker rates the two equal in their backhands. Federer has a one-hander and his "backhand slice... is better than his rival's," while Nadal's two-handed backhand was "a bit of a weakness in terms of variety but has massively improved."
During their careers, Federer has preferred courts with more speed, winning eight times at the All England Club, six Australian Opens, five US Opens and one French Open. Nadal has won the French Open 13 times along with four US Opens, two Wimbledons, and one Australian Open.
While Federer got the edge on volleying, according to Becker, as "he can do pretty much what he wants with his volley," the German said Nadal has a "fantastic eye and this would be an area of his game that is sometimes underrated."
Becker also gave Federer's serving a higher rating, saying he is ''incredibly accurate in terms of picking his spots" and had good disguise. Still, he noted, Nadal has "adapted his technique to make it more powerful and varied."
Nadal, though, is the better mover of the pair, according to Becker. The former No. 1 said Federer's agility is "not quite at the level now that it was ten years ago but still incredibly good for his age." But Nadal, for "someone of his size, and with his muscularity, he is an incredible mover," said Becker.
Becker is a commentator for Eurosport.