I have done a thorough analysis of this; I have a band website builder app that has a MP3 store.
You should look primarily at the fees. Paypal's standard account has is around $0.30 per transaction + 3%. If you Google "PayPal Micropayment" they have an account that is not advertised publicly with lower fees for small transactions. The downside is you have to make a new account to use it, including a different bank account. I spoke to our PayPal account manager, and he said there is no internal plans to change this or promote the micropayments plan.
You should look primarily at the fees. Paypal's standard account has is around $0.30 per transaction + 3%. If you Google "PayPal Micropayment" they have an account that is not advertised publicly with lower fees for small transactions. The downside is you have to make a new account to use it, including a different bank account. I spoke to our PayPal account manager, and he said there is no internal plans to change this or promote the micropayments plan.