I had Shures and liked them but after losing them after having them for three years, I got the ER6s and love them. They fit much better under the helmet, block sound as well and are more comfortable. I was ordering custom earpieces for the Shures and planned on getting them for the ER6s but after using them on trips they haven't bothered me so I haven't got the custom molded ones yet.
As for using Skullcandy earphones, I would recommend getting something that blocks more sound if you want to retain your hearing longer. The Skullcandy earphones and others like them don't block enough sound to protect your ears. You will also end up turning the volume up on your music so you can hear them better further aggravating the problem. With the ER6s or the Shures you won't have to turn the volume up as much in order to hear your music or audiobook.