Are you worried about the actual casting process or "known" 9mm leading and tumbling issues?

Unless you're casting very large or oddly shaped boolits, generally casting is casting. The actual casting differences between a 90 grain 380 boolit and a 120 grain 9mm boolit will be very slight if there are any at all. Of course that assumes no equipment problems.

If you're worried about bore leading, then yeah you may have problems; you may not.

It all depends on what you want to do and how much time, energy and effort you're willing to expend. The most rewarding things in life are seldom the easiest in my experience.

If your 380 ACP gun is your passion, go with boolits for it. Passions, like miseries, love company.