They both generally hold the same meaning and you'll be understood regardless of whether you use one or the other. However, it can be simplified like j'etudierai or something else like j'irai suggests more "certainty". J'irai is in the simple future which describes events that "will" happen in the future Je vais is in the present tense so the here and now. To summarize; Je vais edudier - near future J'edudierai - simple future