Professor Winnie Monsod reviews the academic literature comparing the presidential with the parliamentary systems. Read them here and here. Conclusion: no clear evidence in favor of one or the other system, whether in terms of corruption or economic performance. Parliamentary systems though are more readily associated with structural reform, but also with greater government spending. Professor Monsod concludes that we avoid "indecent haste" in pursuing a shift in system.
When the data is ambiguous, we need to substitute intuition and experience for number-crunching. Look at the recent history of this country. After three People Powers, and nearly a fourth, shouldn't we rethink the idea of a fixed term for the President? Lay to rest the persistent calls for "snap elections" by (con/in)stitutionalizing the "snap election"?
Parliamentary systems are of course fraught with their own risk and sources of instability. It's no magic bullet. Nothing is. But perhaps it would, overall, hasten the pace of development. What do you think?