An additional practical difference is that due to tracking less, that metrics can take much fewer resources allowing you to gain insight that's not practical fr

An additional practical difference is that due to tracking less, that metrics can take much fewer resources allowing you to gain insight that's not practical from logs. I'd expect in a well instrumented system that a single request could easily affect hundreds of metrics. Trying to get that level of information from logging alone isn't practical due to the volume of data it'd require. If you want to track overall behaviour of hundreds of codepoints then metrics are good, if you want to track behaviour for all of your events at a handful of codepoints then logs are good.