Signup flow: synchronous or asynchronous?

So let's say we have a paid subscription signup flow. Usually paid signup flow is implemented in a "synchronous" manner:

• collect details
• click on "sign up"
• wait for card details/charge/etc
• if everything is good, get redirected to to the "welcome" page, otherwise get feedback in the form

However, there is another "asynchronous" way to do it:

• collect details
• click on "sign up"
• immediately get to the "welcome" page that includes a little JS thingie that shows the verification and charge process as it happens:
  • ✓ email delivered
  • ✓ card verified
  • ✗ we couldn't charge your card, please change the card in the profile (link) or contact support (link)

Intuitively it seems that the latter should convert and feel better as it's more "magic", it's faster and 99% of customers will have everything sorted anyway. Those who don't have a bit more stimulus to persist and solve their problems instead of just abandoning the flow. However, the first one is more familiar.

Which one is better?