Low severity, high verbose level:

* Many messages, each message is long.

* High storage requirements but you'll know a lot about any event happening.

The right approach is to apply a risk-management method to your logs. As such, you identify the set of systems that are important for you to keep logs from.

Indeed, it is not necessary to have a one-size-fits-all approach to severity/verbose; instead, you want to crank up the number and level of verbose of logs for important systems and dial it down for non-important systems.