I prefer paying via PayPal. Despite being a somewhat scummy company, their service is a lot more convenient than inputting your information over and over again when using a Credit/Debit card online. Furthermore, having a standardized payment processor is a lot more secure. in the end it's just a matter of preference; sometimes people don't want to give PayPal any fees so they would much rather only use their credit cards. On the other hand most merchants use it because it is standardized and simple to use for both parties (merchants and buyers).
