In the US VCs tend to favor preferred stock over common and debt. Some reasons for that are their ability to negotiate ad hoc details regarding their ownership and involvement (since they tend to prefer being active investors) and because it affords the company some tax advantages that lower costs of employment.

VCs and preferred stock, VC investments

Why do VCs hold preferred stock?

5 things you need to know about stock options - https://www.techrepublic.com/article/going-to-work-for-a-startup-lets-talk-equity/