- Portion control- You're either packing the bento the night before or the morning of. Either way, you're not hungry when you're packing it, so you're unlikely to pack way more than you actually need just because you can.
- Cost effective- You're just not spending money at lunchtime. If you still live with your parents, you're probably not spending money at all (most parents are very happy with this configuration, as they know you're getting good food in the day and will therefore be happier and able to work harder at school). If you live on your own as a student, you will still be saving masses of money by putting dinner's leftovers in a box for tomorrow's lunch.
- Guaranteeing yourself a lunch you actually want to eat- No one wants pot luck as to whether the caf' actually has anything good on.
- Tasty home-cooked food is a godsend if you're having a bad day- You've got some delicious noms to look forward to even if your essay comes back with half the marks you expected.
- Saves time- Especially near exam period when you're using your lunchtimes to study in, having a box of food handy is much easier than having to break your roll to go out and get something.
Good question. The answer is simultaneously "not a lot" and "quite a lot". At the end of the day, it is still just a box of food you're going to have at lunch time. However, there are a few differences:
- The actual box: Bento boxes often have two tiers of shallower dishes than western style lunch-boxes, which allows them to be packed more tightly and is better suited to meals that need bits to be separate, like rice and curry (you don't want the rice getting soggy). However, you can always just use any old tupperware box- it's really the food inside that's important.
- The way it's packed: Bentos are packed tightly with as little air as possible. This means you can use a smaller box, and stuff doesn't move around inside (especially useful if you want to make your lunch look pretty and neat). A popular theory is that the size of your bento in ml should roughly equate to the number of calories your lunch contains if you pack one half with rice, and split the other half into one part meat and two parts vegetables.
- The food inside: Obviously you could just cut up a sandwich and shove it in a bento, but it rather defeats the point. Bentos are often packed with Asian food, especially Japanese, since that's where the bento comes from. Character bentos (brightly coloured food arrangements in the shape of favourite tv show characters etc.) are popular for children in Japan, and though it's not really my thing (pink dyed eggs freak me out), it's a great way of getting children to eat healthy food, or just to be creative.