You have to purchase a lot of specialized materials for both types and they both take up a fair amount of space, making them both relatively expensive and commitment-heavy hobbies when compared to say, reading or cooking. In Hydroponics, some of the materials you might buy include lights, tents, fans, equipment such as reservoirs and grow trays. In traditional gardening you need shovels, hoes, seed starters, etc. Another similarity is that you need to know and love the basics of plant care, such as pruning, starting seeds, and knowledge of the basic nutrients they need.
The differences can be pretty striking though. Especially when you look at a hydroponic garden vs a traditional one, hydroponics can seem futuristic and detached, not connected with the earth. You don't have that same pleasurable, visceral sense that you are connected with the earth as when you are working in a soil garden. For some people, like those living in cities this might not be an option so hydroponics is a great way of somehow connecting with nature even if you cant grab a handful of soil!