Free trial or Refund the first days?

Hey there 👋

I am planning to add a pre-launch subscription plan to https://www.buildpublic.app and give the waiting list users a discount.

I am debating between offering a Free trial or a Full refund for the first days of the subscription.

Which option is better? And how many days should I offer a Free trial/Full refund? 🤔

Thanks in advance 😄