Knots or MPH?

[MikeP]

I have always used knots re speed on the water and that's how my chart plotters are set up but the past few days was talking to several people re their boat speed and they were talking in MPH. I asked a dock-friend what the top speed was on his 53MY that was just sea-trialed and he said "21 and change." HOLY MOLY, I replied, a shade over 18 is the best I ever saw out of our 53 and I always thought it ran pretty well.

Turns out he was talking MPH and I was talking Knots.

So now I'm curious...what do most folks use? I realize knots are "traditional" for boats but so are fathoms and nobody I know, including me, uses that depth measurement.

MPH certainly LOOKS more impressive on the speed readout but, sadly, it doesn't get the boat to a destination any quicker.