Metric is so much easier when it comes to finding the right socket/wrench.The only oddity is that 5.5MM that some Ford and others uses. Both of my vehicles are American made, and have mostly SAE fasteners, but I'v been known to grab the metrics to work on them. 14mm fit's almost exactly 9/16" and 13mm" fits almost exactly 1/2". 10mm is not quite right for 3/8" and 12mm is not quite right for 7/16". There actually a little closer tolerance than the actual 1/2" or 9/16" socket/ wrench so they fit nice and tight.. I do have more SAE tools than metric. I don't buy a metric fastener unless the bolt is captive and I need to. So much easier to remember 3/8" course or fine thread for example, not so easy M10x 1.25.