We recently returned to ADP after using Paychex since at the time they were the only ones to offer an online solution. With that said…PAYCHEX stinks, you cannot imagine how many letters I received from the state saying that their calculations were wrong…or payments were late.
As for which one…you need to remember that the service is only as good as the staff it employees, and each of these companies have regional offices so just because I had a problem with our regional office, does not mean you will with your office.
I like ADP since their online solution is web based and NOT secondary Java Appelet like Paychex…old technology and a pain in the butt.