We have used all three. Authorizenet.com is more commonly known to the consumer becuase they market it - most gateways do not market themselves because most people think that is the only thing they need.
When we set up connectivity with Authorizenet.com it was somewhat difficult. They offer you a test account but you have to sign up with their service first - which I found to be quite redundant. Why did I have to pay them to test their system? Fortunately, someone allowed us to borrow their account for us to test connectivity. I won't comment on their security practices - but they have to be pretty good since they also use the First Data platform to connect to Visa.net, etc. And you know that First Data owns LinkPoint.
With LinkPoint - we were able to set up a teststore & they gave me code that even I could understand. All of our processing is done thru the LinkPoint Gateway for hosting & consulting. We have not had any problems with fraud or chargebacks.
As far as Verisign & their charges - there are lots of resellers out there who offer Verisign at a much cheaper rate. The programmers are just now re-testing connectivity with Verisign I have been putting it off for the past few months.
The biggest problems with them all - you usually go thru resellers to get the merchant account / gateway. So you have to deal with sales people. And then with authorizenet.com - you go to their resellers and then you might even be re-directed over to another party to actually get the merchant account / processor.
The gateway - even though it is a very big part of it - you should also consider the CC processor. And no matter what, keep in contact with your agent - especially if you might go over your monthly volume so your agent can contact the cc processor. This will always help to prevent problems.