There is a reason why the hardest and the most powerful backhand in the game belongs to Wawarinka and not Djokovic or Murray; and when it comes to power, Federer’s BH is as good as Djoko’s and Murray’s or anyone else with a two-hander for that matter. The single hander allows for generation of a longer and unrestricted swing path and if you are hitting it right the contact is ahead of the front foot which helps lengthen the swing even more. All of that translates into increased racket-head momentum which leads to more power being transferred into the ball at the point of contact. Therefore, the one-hander can be more powerful, versatile, and with better reach.
However, the two-hander is much easier to teach to kids and most local coaches do not want to take the pains and the risk of teaching the one-hander to them. Even parents do not have the patience to wait a year before their 9 year old can actually hit more than 2 balls across the net while learning the one-hander. Moreover, today’s game with modern day’s string technology has lead to an insane amount of spin generation which invariably results in balls rising above shoulder level for even the taller players, and playing high rising balls is the only disadvantage of a one-hander.
That disadvantage gets further exaggerated on return of kick-serves and while facing Nadal. The only way to deal with this disadvantage is to play inside or at the base line and take the ball very early and not allow it to rise too much; but slower courts and advancement in string-technology gives the advantage back to base-line players as they get enough time to reach even unreachable balls and return them with a vengeance. Moreover, you need real talent to take the balls really early and not too many players even at the very top can do that. Federer, of course has that talent but in the AO 2017 he was also helped by a relatively faster court which didn’t allow the likes of Djokovic and Nadal to track down every ball which they would have on a slower court.
Personally, I believe that the AO 2017 court speed should be the lower end; and other courts including Wimbledon should become even faster because the string technology is so advanced that practically most first serves can be returned by good players so the possibility of having a Sampras v/s Ivanivisic one shot display is non-existent.