Those that say that one is better than the other have very limited experience. They should not be making claims like those. Over many years (more than 43) I have witnessed first hand top notch students of both Karate and Taekwondo. but there is nothing that can show superiority of one over the other. Everything comes down to the student, his ability, the quality of the instruction he has received, how coordinated he is, and in many cases luck. Over the years, I have also witnessed many students in both Karate and Taekwondo that are really terrible. It is not the fault of the art. It is the fault of the instructor, the student, or both.
My suggestion is simply. find the best instructor no matter which he teaches. Study with him. Avoid any school that has children black belt, sells belt contracts, or tells you that you can be a certain belt level in X amount of time. The belt a person wears should be a reflection of his knowledge, understanding, and ability. It should never be decided mainly on time, money, or politics.
Martial arts training and research over 43 years (Since 1967).
Teaching martial arts over 37 years (Since 1973).