Don't underestimate the power of good earpads. If set up correctly, they can really improve sonic reproduction, and improve the transition of sound from the driver to your ears. Earpads that seal well, that are somewhat thick, that are constructed well, and pads that are properly installed on the headphones (no gaps present anywhere) is preferred.
I found out that putting cotton underneath the earpads tends to absorb the midrange frequencies a bit, causing it to sound somewhat recessed. The better seal you have around your ears, the more bass impact you will have. In other words, the seal with your head to the earpads is deciding factor in how much bass quantity you will have, and how well it will scale at loud volumes. You can have two different earpads that have roughly equal amounts of observable bass quantity at low/medium volume levels, but the earpad that has the greater seal around your ears will preserve the quality of the lower frequencies at greater volume levels. The side with the worse seal will sound kinda flabby (like having the headphones away from your ears), while the other side with the greater seal will probably sound cleaner in the lower frequencies.
I also found out that earpads that are rounded on the bottom (most of the earpads out there), and have little holes underneath for the cotton to breath can also absorb some of the sound (earpads like this). Earpads that are more angled and near the base, like these or these are, will give the sound produced by the driver a more unobstructed path to your ears. That's just my experience.