I only say that working off the following information:
Weight: 9mm is typically 25% heavier than 380
Muzzle Energy: 200 ft/lb (380), 400 ft/lb (9mm)
Cost per 50rd range ammo: $15-18 (380), $10-12 (9mm)
Variety of platforms isn't close. 380s are available in compacts and subcompacts. And that's about it; which is fine, as there's a specific design in mind for that caliber. But of course 9mm also offers hi-cap combat type pistols, carbine rifles, 1911s, etc.
Overpenetration is not a concern with a well placed shot from either, provided you're using quality JHPs. Use what you like. A 380acp can be a perfectly adequate and convenient to carry round. My only point is that it's not ideal for me. The cheapo that I am, I probably just hate paying 50% more for a round that's half as powerful and less versatile.
"The Future is Unwritten"