Wheels on a sports car. Shoes with a suit. Painted shutters on a house. These are all things that make or break the cohesiveness and coordination of a set of objects. It’s no different with a watch and its strap. As long as one isn’t attempting to make some kind of statement, it’s of utmost importance to match a watch to a strap.
This doesn’t just mean that the strap needs to have a coordinating color with the watch; the strap needs to *fit* the look of the strap. It may seem like a no-brainer, but strap thickness and padding have a lot to do with how proper the watch appears to be. A super thick canvas strap on a Rolex day-date looks out of place, while a thinner more tapered animal skin helps keep the look refined and sleek. A Rallye strap may look out of place on a dress watch, but it looks perfectly at home with a chronograph. And depending on how OCD you are (I am…) a strap with contrast stitching looks best on sports watches and can look out of place on a dress watch.
All of this is certainly all about personal preference, but in my experience, the best-looking watch straps never take attention away from their timepiece. Just remember, there’s a strap out there for every watch.