Python and Java are equivalent in the sense that both a Turing Complete. Is there a similar equivalence between all musical instruments which makes choosing one over another a purely arbitrary decision? I don't know but I suspect not. A pair of bongos seems to have much less to offer as an instructional vehicle for learning about music than, say, a piano.

EDIT: Setting aside the above argument for a second, there are practical considerations too that make the choice of musical instrument a non-arbitrary decision. For example: the cost of the instrument, its portability (important if the band decides to tour) and of course the availability of instruction.