A client is using CardService International, which is expensive and its features are lacking. We are looking at authorize.net and verisign (now paypal?) anyone have suggestions or feelings of which system they prefer? sincerely
I definitely prefer authnet to verisign. Verisign is very expensive and there isn't any major benefit to using it. Authorize.net is more widely used than Verisign at a cost that is usually much less than half of the price of verisign. Authorize.net using the AIM method is the best way to go.
I'm assuming you are using the Linkpoint gateway since that is what CardService likes to push. You should read this article which compares LinkPoint, Authorize.net, and Verisign. I agree with Jaime that Authorize.net gateway is probably the best way to go. Integrating their Advanced API is pretty easy and the gateway as a whole is rock solid.