The key to selling more on eBay is appealing to a large number of buyers. Accepting multiple payment options is one way to do this. The more payment methods you accept, the more likely you are to find a buyer.
The question is whether or not you want to do business with the broader base of buyers. There are plenty of above-board buyers who prefer to pay with money orders and cashier’s checks, but there are also fraudulent buyers who will attempt to pay with fake money orders. You must decide how much risk you are willing to accept.