Spreadshirt+PayPal

If you just plan on using paypal to get money from spreadshirt and then sending that money to your bank account, then either account will work:
http://www.paypal.com/cgi-bin/webscr?cmd=_display-fees-outside

The business/premier accounts offer a bit more options if you plan on doing more accepting of payments/selling.

You can always start out with the personal account and if you find your needs change, you can upgrade that account to a business or premier pretty easily (PayPal will remind you often of how easy it is to switch and why )

Thanks for the info Rodney; though it seems like I have no choice but to go with the premier option since I'm pretty sure most shoppers these days use either their debit or credit.

Oh, I thought you were just using paypal to collect payments from spreadshirt?

If that's the case, you can get a personal account and still get payments from spreadshirt (spreadshirt processes the payments from customers and just sends you your commissions via paypal)

If you are accepting payments directly from customers, then yes, you'll want the business/premier account.

Oh! My bad, I should have been more thorough with the question. Thanks for the heads up!