The sentences are essentially the same, with just a difference of tan or tanto. Tan is used to compare two nouns with ad adjective or adverb, in this case Marcos and tú are nouns and the adjective being compared is how well he plays. Tanto, on the other hand, relates to the amount of something being compared, for example: Tengo tanto dinero como Alicia (I have as much money as Alicia).
