Best type for sound...in-ear or ear covers in your opinion

Well purely in terms of sound, you get a lot more for your money with full-size headphones. You'd have to spend hundreds of dollars to get an IEM that sounds comparable to a $60 Grado SR-60.

Whether you get full-size or in-ears really depends on how you will use them. In-ears are very convenient and portable, obviously. Also, the isolation is great for people who use their iPods on trains or planes.