What do you think iz better?Going to a martial arts school that teaches more than one style?
Learn two styles initially. Learn a striking style and a grappling style. Follow that up with filling in the gaps in those styles. For example, should you know classic muay thai and brazilian jiujitsu, add boxing so you can punch competently and wrestling or judo to improve your takedowns. Its about being complete and well rounded. You can specialize, but if you can't do a certain style of fighting at all, you will most certainly lose.