Carbon fiber and titanium have many of the same strengths and weaknesses. They are both sturdy, long-lasting materials that are lightweight. In terms of weight, they are comparable to the point where if you are holding a ring in each hand, you won't notice the difference. Technically speaking, carbon fiber is lighter than titanium.
Both materials offer a wide array of customization and design options so that your wedding band can be unique to you. For a piece of jewelry that you'll wear for the rest of your life, that is an important consideration.
While they are both typically skin-safe, people with serious metal allergies might have an easier time with a carbon fiber ring than a titanium band. However, both options are affordable and body-safe.
Carbon fiber is easier to work with than titanium which also means carbon fiber rings can be re-sized if needed whereas the latter cannot be re-sized.
Carbon fiber comes in a natural sleek and shiny silver color whereas titanium is more of a matte silver. The color alone may deter you from purchasing a carbon fiber or titanium wedding band.
Ultimately, the best wedding band material is the one that works best for you and your lifestyle. If you're looking for a durable ring that you don't have to worry about damaging, then both carbon fiber and titanium will work well for you!