The issue of what is ‘good English’ is a complicated subject for English Teachers. In language use, what is coined ‘better English’ really depends on the values unrelated to an understanding of grammatical structures. The example above, use of I or me, the form of the pronoun is either in subject or object position. The grammatical point is- is than being used a conjunction as in Mary can run faster than I can run or as a preposition as in Mary can run faster than me. In the latter, than is being used as a conjunction- a form that connects two clauses. In the former, English tends to use object pronouns (e.g. me, her, him) after prepositions. Both forms are correct, neither form is better English than the other.