Choosing the right luggage for your trip is one the most important decisions of the vacation planning process. Obviously if you want to go backpacking through Europe you are not going to be bringing a suitcase and if you are packing suits for a business trip you are not going to throw them in a backpack. So I guess the best question would be, "What are my options?"
Option 1: The Suitcase
The days of the hard suitcase are over. Now everywhere you look its fabric suitcases with multiple zippers for various compartments. They are for the most part light weight and very convenient. The most popular bags seem to be the ones that have wheels and a retractable handle so you can simply wheel you bag down the hall instead of carrying. The wheels can damaged despite and no one wants to buy a new bag just because of the wheels so you might as well learn how to replace your luggage wheels. An average bag will run you about $ 40 dollars and sets of 4 or 5 decent quality bags can be had for about $ 150.
Option 2: The Backpack
Visiting hostels around the world? Taking a short trip to see some friends? Just want to look cool? Then the backpack is for you. There are many variations of the travel backpack. There are very large ones that act almost as a duffel bag, very small ones that can be used as a daypack for short trips from the hostel and the standard sizes that come with multiple compartments for your water, guide books, clothes, etc. Strapping a bag to your back is the only way to travel between multiple destinations and you'll beat it up a bit with all of that traveling so buy a good one. They can be had for as cheap as $ 40 on sale but most will run you between $ 90 and $ 200.
Option 3: The Duffel Bag
Ah the classic duffel bag. Duffel bags have come a long way since the classic tan one compartment army bag of old. They still have one large main compartment but most have a couple more on the sides for easy access to water and books. They look a lot cooler now a days too and some can even convert into a backpack. Use a duffel bag when one large main compartment makes sense. Ski boots for instance would need such a place. Duffel bags come in a lot of sizes so $ 30 to $ 90 is a good bet.
Just remember to think about your particular travel situation in advance because the right bag can make the perfect trip.