I would say to use Squadcast, the configuration is easy, provides a lot of features such as war room, RCA tracking postmortem, RBAC and they are quick to add features on request as well, recently I asked for custom on call reminders and I am sure they will add it really soon.

Disclosure I work at Splunk and VictorOps is a Splunk product. But I would suggest in addition to trying the others adding VO to your list. It's important to note that some of the tools are designed as Incident Response tools, others started as mass notification tools. For on-call stick to those designed for incident response.