Your body needs the energy to properly digest food. So to get the most out of the nutrients you consume and your workout, eat before exercising or 30 mins after fruit, two hours after veggies, three hours after grains four hours after meats and poultry.
So it's not a matter of value, it's a matter of what you need it to hold. And a matter of affordability. The movies will be the biggest space hog. So if you only put the movie you want to watch next on the iPod touch, so one (or two) movies at any given time, you will have more than enough space with either 16 or 32 GB. People watch movies once (twice if it's really good); they do not watch a movie over and over again like listening to songs.
500* songs in a single 2gb iPod shuffle of 3rd gen or better. Actual capacity is lesser. *Apple estimated the song capacity of the first and second generation iPod using the 160-Kbps MP3 format. These files are larger than the 128-Kbps AAC format used to estimate the capacity of subsequent iPod models.