Suitcases are an investment that allow for smoother travel as you navigate bus, train, plane and uneven streets. I love using backpacks or bags that allow for a backpack conversion so my hands are free, and I'm forced to pack lighter.
Recently, I upgraded my Patagonia MLC and added another backpack of the same size to my collection. Use a company that has a guarantee, such as L.L. Bean, Patagonia, or Eagle Creek. For a well thought-out weekender bag, check out the Rhodes duffel (for men) and the Catalina (for women) at Lo & Sons.
The high price on a good quality bag may initially seem unreasonable, but if it lasts for years and serves you, rather than weighing you down, I'd say it's worth the investment.