Either can be good for you, and either can be made at home. Of course, the reverse is also true--either can be bad for you, depending on what's in them.
If you want granola bars, try to find ones that have quite a bit of fiber and protein in them, because those will keep you full longer and are more likely to be more nutritious than the others. Just be careful because granola bars can be loaded with sugar, which is why making them at home may be a good idea if you plan to eat them often; and I understand if you do, being a college student myself.
Sometimes convenience really can make or break your diet when classes are in session.
As for trail mix, even when making it at home, just keep your portions in check. Trail mix is delicious and filling, and it's made with mostly calorie-dense ingredients like nuts. I'd probably weigh an ounce or so (or if you want more, at least put each ounce into individual baggies to keep track of how much you're eating) as a serving, maybe more just depending on what you put in it. Some suggestions for ingredients would be nuts, dried fruit (and it doesn't have to be raisins! peaches, cranberries, cherries, apples, bananas, strawberries, etc.), and chocolate (of course!).
Whole foods are better, of course, but in the end, we have to do what works for us. I always try to have some convenience foods on hand for those hectic days, and to keep in my backpack; what I bring tends to be way better than the vending machine options on campus. Fruit is also a good snack that's fairly easy to carry around, depending on what it is. Cheese sticks are another, and whole wheat crackers are good too.
Edited by: HEALTHYFOREVER4 at: 7/25/2013 (01:37)