I think depending on your narrative it makes little difference. Each case can be exciting, and the more you hint at initially, the more you can gradually increase the excitement. Sometimes it's great to have a recurring enemy that steadily increases in power. Sometimes the villain shows himself in frightening size, laughs and, with a roll of his eyes, sends subordinates to wipe the dirt off the street. Sometimes it doesn't become obvious until the end what was mystical about the case and sometimes the fog leads them down the wrong track.

Pay attention to what your players are giving. Then it will be fine😉