I think great variety is very "aesthetically pleasing" and more importantly, very effective on the backhand side. Let's not forget that most players today that hit the two handed backhand
primarily ALSO HIT A ONE HANDER in appropriate situations, such as when they want to hit a lot of slice, or hit a good approach shot, or feel stretched out wide. So, those players have great variety and the opponent doesn't know what's coming next.
This discussion of EITHER the 1 handed backhand OR the two handed backhand ignores a reality. It's NOT one or the other, in that it is often BOTH the one handed backhand and the two handed backhand that is most effective and required.
I for one, love to hit the two-handed backhand, especially when rallying during a long point when I am near the center of the court and want to drive shots deep, but then I mix in a lot of one-handed slice shots with a lot of spin that take my opponent wide left and right, and also forces him to often have to move forward very quickly. I constantly mix it up so the opponent can be caught surprised by a two handed backhand drive. I can do a whole lot more with my backhand than my forehand because of that increased variety, though I tend to be a little more offensive with my forehand.
Two-handed backhands can be exceedingly difficult to read and they can't be attacked very effectively with high bouncing topspin shots. When you can hit BOTH the 1 and 2 handed backhand, opponents have few options when trying to "attack" the backhand side. There are no weaknesses left to exploit.
Even someone like Federer has an attackable one handed backhand on clay, because he gets in trouble against players that can generate hard shots with a lot of topspin that constantly force him to hit it near shoulder height. Players with good two handed backhands can handle such shots much more easily.
One can have the ability to hit the one handed backhand volley really, so it's good to have this ability to hit BOTH. So, players like Murray and Wilander in the 80's mix it up wonderfully. Even players like Borg and now Nadal often mix in one handed backhands (especially Nadal when he seeks to hit several slice shots in a row).
Therefore, especially now, you have 2 big categories in terms of the backhand:
1. those that hit the one handed backhand exclusively and can't hit the two handed backhand.
2. those that primarily hit the two handed backhand, yet can also mix in plenty of one handed backhands also, which provides a huge amount of variety, with the inherent advantages of both types of backhands. Depending on the situation, such players adjust and decide whether to go with a one or two handed backhand.
See examples here of Wilander, Murray, and Nadal. This will likely will continue to be the dominant trend of the future in terms of the backhand:
1. Wilander:
http://www.youtube.com/watch?v=Efmy72bXH0c (thanks to TW poster Krosero)
2. Murray:
http://www.youtube.com/watch?v=3g9XC5nkjh0
3. Nadal:
http://www.youtube.com/watch?v=YILDVCr_WkQ
and
http://www.youtube.com/watch?v=lprXfmylnOw
See a lot of great two handed and beautiful two handed backhands here:
http://www.youtube.com/watch?v=zdlep5PkJ9Q
Even Borg, who was famous signature two-handed backhand would hit many one handed backhands, especially at Wimbledon for example.
If you hit only two handed backhands, do yourself a favor and add the one handed backhand. It's a lot of fun to hit, but don't rely on it all the time. Pick your spots accordingly and don't forget the hard hit 2 handed backhand that can be very difficult to read. You can changed directions with it at the last moment and your opponent will not know what's coming next, since you have a one-hander as well.
