While you will likely hear many who clamor that you do "This Art" over "That Art" for "This Reason" or "That Reason", it is more important that you focus one what YOU enjoy most of all. TKD is fine. BJJ is fine. I don't care much for either of them, however that should and hopefully means absolutely nothing to you. If you will be holding a black belt in each style, I'm not sure why you will be making the choice if you enjoy both of them. Talk with both instructors and see if you can fill any assistant instructor roles in order to possibly get a break in tuition and hopefully continue both, if that is what you choose to do. If such an accommodation cannot be made, do not let biased third parties whom you do not know try to persuade you to make a decision that you, yourself, would not make of your own accord. If the issue is not about tuition paid to either school, but rather the cost of travel, you should endeavor to make such travel possible. Either get a part time job or a full-time job (if you are in school) in order to finance your training. Good luck!