I'm far more likely to make an immediate donation to an online contribution request if a PayPal option. Degree of inconvenience to get up, get credit card/check, type info. Many will skip - or delay and forget. PayPal takes seconds to send.
If haven't used, PayPal is preferred method of eBay payments - stores personal/business credit card info, and/or checking account info - to generate instant payments when you request. Sign-in and send. Doesn't forward your card info. No need to type mailing address as auto-populates.
Might make sense to add PayPal as an option for charitable, PAC and other giving (when allowed in state law). Even if your ecommerce system has better rate - end user likely has to type lines and lines of data. Consider convenience of PayPal and clear potential to capture contributors who may not otherwise give. Make it easy.
Ben Martin's blog relays a friend/AE/blogger's wife in a car accident. Encourages contribution to help family - with online PayPal donation form. Ben makes it easy to give. PayPal can potentially improve your association fundraising activities.