Prefer knots for flying. Although grew up with feet/inches/yards, the metric system is just fine--base ten arithmetic works every time!
Don't mind visibility in metric but I do prefer the FLs the way they are (in other words not in meters). For me it is just simpler to use. Always a bit of a thinking exercise when flying into or through China's airspace. Much easier now going through Russia's and I might be wrong about this, but it seems the controllers like it as well.