The verdict
For a small B2B team whose buyers research tools and problems online, pick Reddit Ads. A capped test is cheap, the intent is clearer, and writing a good ad takes a writer, not a video crew.
Pick TikTok Ads for a direct-to-consumer or e-commerce brand that can produce native-style video and wants to reach a younger audience. Commerce tools such as catalogue-based product ads help shops.
If you sell a complex, high-ticket service to an older buyer, TikTok will probably cost more per customer than LinkedIn Ads or Google Ads. Whichever you choose, set a fixed budget and a stop rule, and judge on cost per customer.