I think you need to look for:
1. Unifications. All aspects of the monitoring should be done by one or multiple tools. As an option, integration between tools should be possible.
2. Plug-in based or open architecture. Open Source will be a huge plus. In this case, you will have community support, and hiring the expert for widely used technology should not be the issue.
3. Tools should have quick support - monitoring could go down when you really need this. Open Source tools allow you to have a big market of engineers with good expertise.
4. Agree with other comments - ROI is very important here.
The ability for the solution to correlate data from across the enterprise to remove noise in alerts, and for the alerts to be able to trigger automation to remediate a known problem/incident.
I would propose to look at Infrastructure monitoring from a different perspective. The corollary I would use is to equate infrastructure monitoring to a big data problem with the need for automation. In today's world we have many infrastructure devices that transmit a large amount of data or telemetry and the key to quick automated response is to look at adjacencies and quickly determine corrective action. I suggest injecting the telemetry into an infrastructure data lake and apply some ML & AI applications to determine issues and automation to quickly solve. The amount of data produced has become daunting and I suggest taking a data driven approach instead of siloed Infrastructure monitoring tools.
Peace of mind, Easy of use, ROI
It's integration, helping to improve management capability, and ROI, how does it drive value (this include price).
Our most important criteria include price, compatibility with our existing infrastructure, HIPAA compliance, and security.
With the security issues associated with SolarWinds - are people switching to other vendors? Which ones are you switching to?