1) It is more convenient to see my eBay credit card charges in one central location, rather than having to search here and there for various transactions.
2) The "My eBay" page indicates "paid" as the transaction status, whenever you use PayPal. This is quick and convenient, plus you receive an e-mail receipt for each transaction.
3) I like the option to debit from my bank account for small items (which most of my eBay wins are). This frees me from accumulating too many cc charges.
4) Some sellers are enrolled in the eBay protection program, though only some are. But there is always a measure of protection through PayPal, which is good when I debit from my bank account.
5) PayPal is very convenient when you win multiple auctions from the same seller, or when you have another transaction with the same seller, as it retains the seller's e-mail address and makes for faster processing when typing in information.
6) I also find that most sellers who are accustomed to dealing with PayPal tend to ship immediately upon receipt.
When you use PayPal with a credit card, you will find that your credit card company only receives the info that it is a PayPal-posted eBay charge. They have no info about the seller, and since it is a third-party charge, they will take no action, referring you back to PayPal. But I would prefer that PayPal (now part of eBay) has my cc info, rather than the seller.