Over the past years iPod and iPhone capacities have gotten larger and larger. Throughout these times I still advise friends to stay with the smallest size models in the iPod and iPhone lines. You may say, "Isn't larger the better?" Well in this case, that is not necessary true. Especially when people store mostly audio tracks: music and podcast, on these devices.
Some say, "I have a collection of several thousand tracks, how can I store them all on an iPod or iPhone with small capacities." My question to that is, how many hours do you have in a day to listen to audio tracks? For most that is 8 - 10 hours during a normal day.
My suggestion to these people who I recommends to buy the samllest size iPod or iPhone, is to use the "Smart Playlist" feature within iTunes to help select a set of fresh music tracks to synchronize to the iPod or iPhone each day or however frequent.
This above is just an example of the filters (criterions) to use for your Smart Playlist. Of course your filters may be different, but the goals are to not choose too many tracks and to always select new tracks each time the iPod or iPhone is synchronized with iTunes.
The first filter is to choose the list of tracks that had not been played in the past day. You can increase these if you do not mind listening to the same track as the day before.
Next, among these tracks I choose only the ones that I had given a rating of more than 3 stars. How you use the rating system within iTunes is up to you. I personally use it to mark tracks that I really like to listen to or will want to appear on my iPhone.
The "Limit to" checkbox I set the total selection to fill 8 hours and these tracks are chosen randomly. I also checked the "Match only checked items" checkbox, because when I rip (import) a CD I normally rip the entire CD for archive purpose, but I may only like one or two tracks on the CD, so I only check the tracks that I like and leave the others unchecked.
The above Smart Album is only about 740MB in size which means that even for a 8GB iPod I still have a lot of room for customized playlists (ie. "work out"), podcasts and video files.