Class D is more efficient. If you don't care about the physical size of the amplifier and if the crossovers aren't a deciding factor(which I'm unsure of since you didn't respond to that matter) then I can't tell you Class D or Class AB is better. For me, D is better because I want to run as much power as I can without upgrading my alternator or adding batteries. Amplifiers don't all sound the same, but you can't truly know that without trying a number of amplifiers. I promise you, my Class D amplifier is not lacking in sound quality, so don't believe it if someone says they can't sound good.