I’d say it depends on your long-terms goals. If you think you have a realistic shot at the draft, and want to pursue pro ball following school, then I’d play on a dedicated summer league team. The experience and exposure will help. If you’re sort of on the fence about where your ability is and what you’d like to do, then playing in a less structured men’s league and doing the internship is going to be a great option.
Honestly, either way, you’ve got good options. My thought is this: Our window of opportunity to play baseball is so small (early 20s), that if it’s something you really want to pursue now is the time to do it. The “real jobs” will still be there when baseball is over.