Splunk On-Call has proved to be a great help in incident response within my organization. With the scheduling and assignment feature it is never in question which engineer is tasked with each assignment/incident. Being able to quickly and easily access all relevant logs greatly expedites incident resolution time. I would argue that the larger the environment and incident volume, the more important a tool such as this will prove to be.
VictorOps support has proven excellent for us. Because it is such a widely used tool, there is a lot of documentation on usage, and a large community of users to lean on. Also, many engineers have had experience working with VictorOps already, and the tool is so easy to setup / manage that much support isn't really necessary.
Splunk is more intelligent, easy, and faster compared to other tools in the market. Easy to configure, and customization can be done easily. It's more user-friendly, and it adds more value when I mention about the navigation panel. Multi-level escalations and root cause analysis is done in an intelligent way. Troubleshooting is faster.