Switching to a New Debit/Credit Card Processor

My credit union is presently exploring switching to a new debit/credit card processing vendor.  Three vendors have responded, Vantiv, First Data Resources (FDR) and Fiserv.  The three have also been onsite for a presentation.  If you use/previously used one of the three vendors, I am looking for input you may be willing to share so that we may consider actual experience in the decision process.   Would you also include your asset size, the approximate number of debit/credit cards in your database and if you are a Harland user?Asset Size -$3.1 billionActive Debit Card Base -115,000 cardsActive Credit Card Base-46,836 cards and 63,852 cards