Steampunk vs Cyberpunk
If you take the anti-authoritarian/anti-establishment attitude of ‘punk’ and combine it with either futurism or Neo-Victorianism, I believe that’s where you can start defining these two genres. Both evolve out of the mechanistic oppression of their times, and reflect the zeitgeists of the eras, yet both are also relevant to our dystopian, Machiavellian current times, and express the subconscious anxiety of man’s changing relationship with machines. The result is synthetic nostalgia for a past that never was and the future that probably never will be.
Unfortunately both have suffered the same fate as many other genres once popular culture gets a hold of them: commercialism - the commodification of everything.