The verdict
For a small team that sells to consumers or to a wide group and wants to test demand fast, pick Meta Ads. The reach is large, click-to-message ads are available and Advantage+ campaigns automate more of the setup.
For a team whose buyers discuss your category in identifiable communities, pick Reddit Ads. It suits technical, niche and hobby topics, where honest, specific ads can work.
If you target narrow B2B job titles, neither is ideal. Meta is weaker on titles than a professional network, and Reddit is weaker on scale. In that case I would run a small, capped test on each with the same goal and budget, and keep the one that gives the cheaper customer.