Most efficient payment UX model

I am trying to understand which payment UX model is the most efficient.

It is about an mobile app providing matrimonial services. I can think of two options:

  1. The user enters all user details and then on submit we show him the payment options.
  2. Make the user pay first and then move to entering user details.

Which method has the maximum chance for the user to pay or abandon? Are there any stats or analytics explaining this?