Paypal is very good if you sell your own products, it's a ready-made platform which is easy enough to install without technical knowledge.
In my experience, Paypal is not suited for a large volume of transactions: it becomes very risky, and Paypal has the habit of blocking accounts at the slightest complaint, justified or not. Keep in mind that Paypal is based in Luxemburg, and they are allowed to freeze your assets for several months according to local legislation.