Yes, methyl benzoate and phenylacetic acid have the same empirical formula, but just because two substances have the same empirical formula does not mean they react the same or have similar properties. Far from it. For example, acetic acid and glucose have the same empirical formula. Why not put vinegar in your coffee or sugar on your salad? What matters is the actual molecular structure of the chemical. All the empirical formula indicates is the ratio of elements. It does not indicate how those elements are arranged.
An aside: There is a way to make P2P and/or meth from methyl benzoate, but it involves Claisen condensations and carbonyl reductions (i.e. a completely different mechanism than via phenylacetic acid). UTFSE to find out.
