I realize that iPods are the most popular mp3 players, but honestly I haven't have my own.Admittedly, I did not bother to research the question myself. My friend just told me :"If you are looking to purchase a Nano, I highly recommend the new third generation over the second, simply because of the added video feature and twice the memory for your money." Here are some useful imformation about the gen3 nano's compared with the gene2 . Hope this helps and waiting your completment.
Apple shortened the body in order to limit breaks due to the former generation flexing in people's pockets and bags.The longer nano was prone to bend (and sometimes break) when people put them in their pocket and sat down or moved around;
Sound quality is not significantly improved from previous models;
There are some changes in the components and software that do take the screen brighter and allow you to do more things, including watch videos and play games.
Apple's software is still a weakness with very limited direct control over your device library and few file options.
A design flaw--the headphone jack is on the bottom.As a result, the dock connector and headphone jack are so close together that it's hard to squeeze the sides of USB connector to disconnect it while the headphones are still plugged in.
So, if you are an early adopter, be aware of that.
Light bulbs you shouldn't buy
There are plenty of dimmable LED light bulbs, but make sure you don't buy the ones that flicker when you dial them down.