Bigger isn't always better. What's going in the bag and how far you have to carry it are major considerations when deciding between one big bag and two (or more) smaller ones. When I'm traveling on my own, I opt for several smaller bags that are easier to manage, even if that means I have to make more trips.
To pocket or not to pocket? One of my favorite bags has pockets that surround the outside. Great for car travel, this bag allows me to keep necessities close at hand. It's not so great for a day in New York City, though -- those pockets that keep everything accessible to me keep them accessible to passersby as well. Choose your bag with both your transportation and your destination in mind.
Strappy situation. The more you're going to load into your bag, the more important the straps become. I have several bags that can hold a lot, but whose straps aren't wide enough to distribute the weight well; when I carry them, the straps dig into my shoulder. The straps are sturdy enough that they're not likely to snap, but they're less than ideal for transporting the bag more than a short distance. If you're going to load up a bag, make sure the straps are up to the task and that they won't dig into your hands or shoulders when you carry them from Point A to Point B.
Don't be fooled by the original purpose. I have a bag that is perfect for storing electronics and their various cords. Its original purpose? A cosmetic bag. I don't think I've had that many cosmetics in my entire life, and repurposing it created a travel storage solution that provides both portability and accessibility.
Whether the container has a home in your home or is temporary travel storage, matching the container to the task, your tastes and styles helps keep you organized, no matter where you're going.