The verdict
For a small B2B team, I'd pick neither right now. Skai is an enterprise tool, and I would not look at it unless the ad budget is large and a team will run it daily. For modest budgets, the native ad platforms or a lighter tool such as Optmyzr or Madgicx are the sensible route.
If you must choose, I'd pick Customers.ai when you are an e-commerce brand on Klaviyo who wants to test visitor identification on the trial. I'd pick Skai when channel sprawl and retail media are the actual problem. They can also sit side by side, but only at a scale where both pay back.