Required registration/login for checkout. Should you use a popup on the previous page, or have the login/register on the checkout page?

Question

I am requiring a login/register for my checkout (because the user is purchasing a premium account for my music site).

I have seen 2 main ways to do this:

1. On the page linking to the checkout page (such as the page outlining the benefits of the premium account), have a login/register popup. Examples of this method include Pandora, and Reddit.
2. Have the login/register be part of the checkout page (either a single or multipage checkout process). Examples include Pythonanywhere, and Rackspace.

I only have 3 steps: login/register (unless the user is already logged in), choosing payment type (Credit Card or Paypal), and filling in payment info (either on the site for credit card, or on the Paypal site). Any advice on what situation would call for each method?

EDIT: added that I have a "choose payment type" step in my checkout.

Answer 1

Why even present it as a registration? If you simply make the fields you need part of the process simply tuck the password fields at the end. Add a simple statement like "enter a password for easy access immediately after your purchase"

This way the user is simply entering information they normally would at checkout with whatever additional info you need.

If the user has a login, you can place a link at the top "Already have a login?" Clicking the link swaps the form with login fields. Collect any additional info required post login.

I hope this helps.