Metrics only make sense when you're using them in everything else. Your vehicle's odometer, rangefinder, maps, etc. Otherwise, you're spending lots of time converting to a system that you don't use for anything else. Metrics offer the benefit of multiples of 10 which can be helpful if you're trying to quickly calculate something mentally in the field. But with a good scope, they're not quite as precise. And then there's what you're used to.