I would stick with Authorizenet and a real shopping
I have a big problem with PayPal because if you
ever want to sell your business, the buyer will
value it based upon the recurring billing.
PayPal will not let you transfer the account to the
buyer so the business value drops.
On the other hand, if you were using a real shopping
cart, all you would need to do is to change your
Authorizenet account to the buyers Authoriznet account
and the shopping cart would send the money to the
new buyers account.
Both PayPal and Authorize.Net are cc processors rather than shopping carts. It may be possible to add a PayPal button that will charge a reoccurring charge. If you want something that will automatically manage the subscriptions, you will need to code something.