Be weary of promises for "full benefit-payroll integration" for a company your size - from any vendor. The fact is that the insurance carriers typically will not provide EDI files (automation) for benefits until you have 100 enrolled employees.
When Gusto, Zenefits, a Broker, or any other company is promising that type of integration they have someone transferring data on the backend. It might look fully integrated, but it is not. I have seen many problems with process from Gusto and Zenefits in particular.
Not only is there an opportunity for manual data entry error, the people entering the data have to keep track of differing business rules and state laws.
For example, your company might make employees eligible for benefits the first day of the month following 60 days after their hire date. The person (low level employee) at Zenefits might interpret that as after 90 days or 2 months. With that error an employee might be promised benefits under your policy or SPD and not receive them. If a catastrophic medical event were to take place your company could be liable. I have seen this exact error take place.
I hope this helps. As mentioned earlier, I am happy to discuss or answer questions.
Ian