The asymmetrical design was pioneered by Pinarello and then taken to the stupid extreme by Cervelo with its BB-Right concept. It is stupid, stupid, stupid. If you go to the BB-Right website (dot org, I think), you'll see a load of pseudo-technical stuff there but nothing that explains why, that makes sense. Most people who read it have their eyes go wonky and then nod, which is what they want.
Asymmetrical in a marketing brochure sounds so much more thought-through than symmetrical.
Asymmetrical sounds like weight is reduced where it is not needed.
Asymmetrical sounds like stuff that is so technically perfect that it doesn't have to be aesthetically pleasing.
Asymmetrical is Bullshit.
They will argue that the chain tension requires higher strength from the chainstay on the right than on the left. However, both are strong enough and has been since the chain-drive bike has been invented. It is Bullshit.
They will argue that the way torque enters the BB via a pipe on the left and is fed directly into the chainring on the right, requires asymmetrical technology.
It is bullshit. The use of the word "technology" is Bullshit.
I once did not have a black spoke of the right length to fix a broken wheel with all black spokes and gave the customer a silver spoke in stead. I told the customer he just got, at the price of normal "technology", asymmetrical pigmentation technology. He loved it.
But it is Bullshit.