Different travelers have different needs. Different destinations have different challenges. In as much as we would like to have a one-size-fits-all solution, every experience is different and would need to be complemented with the right tools and accessories. One big consideration is and always will be the kind of luggage you will bring. It essentially depends on personal preferences and comfort, but sometimes it's better to have one kind than another. Let’s take a look at the pros and cons of each bag.
Each of those options has pros & cons.
Duffel bags can be a handy alternative for the casual traveler. They tend to be lighter and are sometimes easier to maneuver. If the duffel bag has wheels, it may be a reasonable option. A big duffel bag on wheels is narrower than a medium or large rolling suitcase and it could even be a little easier to roll around a crowded airport.
Duffel bags are roomy and flexible, so you are able to pack a lot more things in there than a regular suitcase. There are also more organizational options in terms of more side and inner pockets for you to store your stuff in.
Duffel bags can help give a feeling of freedom to your travel experience. A duffel is great for a totally casual trip, especially if you have a lot of shoes or a lot of power cords or odd shaped items.
This seems to be the most popular method used by most travellers. If you’re doing a more formal trip, or you want to wheel your bag instead of carry it around, you’ll probably want to stick with traditional luggage, and use the rolling suitcase. Also it can usually be locked to provide some security.
On smooth surfaces, suitcases are easy to use. Good rolling suitcases can make it feel like you're carrying next to nothing. If your travel plans are predictable and you know exactly where you'll end up, a rolling suitcase is probably the best choice. Duffel bags can be painful on your shoulder after a few minutes, but you can pull/push around a suitcase for as long as you need to. But when you encounter grass, sand, or stairs, however, then it's going to be a bit awkward. That's also a concern when staying in hotels that don't have an elevator.
Before we go into the gritty of what your next purchase should be, here are some general tips if your destinations are as varied as your preferences.
Transportation: If you'll be riding cars and chauffeured everywhere, then a rolling suitcase won't be a problem. But if you'll be getting on and off buses, trains, boats, and bikes, then a duffel bag will be more convenient.
Itinerary: If you have a place to keep all your things, it doesn't matter what luggage you bring. But if you'll be moving around a lot, then consider how tired you'll be carrying your luggage around.
Infrastructure: Pavements and smooth floors are perfect for suitcases. Otherwise, carry a duffel over dirt, cobblestone, brick, and up buildings with no elevators.
I hope this can help you to choose a suitable travel bag.