In my experience, Google still reigns supreme—not just because it's Google, but because users typically go there with intent. When someone searches on Google, they're often actively looking for that product or something similar, meaning they already have an interest in buying.
Now, think about Facebook. Do you use it when you're in "shopping mode" or ready to make a purchase? Probably not.
To outperform Google, you'll need a killer ad and an irresistible product deal (again, speaking from my own experience).
That said, many factors come into play—your audience's age, gender, interests, etc. The best approach is to run A/B tests on both platforms to see what works best for your specific product or niche, as there’s no one-size-fits-all solution.