There are many factors that will come into play when deciding on one of the two different accoutrements.
Why Leather?
Many people are allergic to the metal that most watches are made from, some people are even allergic to gold and silver, still fewer people can only wear platinum due to the inert quality of the metal. Rather than forking over the amount of money it would take in order to purchase a platinum wrist band, these types of people are more than likely to opt for the leather band, and probably the band that goes under the watch itself holding that metal away from the skin too. There are a plethora of different leather styles that can go with just about any style of watch you can imagine, from a slim, narrow leather band for the elegant slim line watches to thick impressive looking bands for the large multi-function watches.
Why Metal?
Some may even opt for leather for their dive watches, however most would probably opt for the metal band because of the imperviousness to water and the ease of cleaning and drying. There are many styles of metal watch bands, from the stretch type to a clasp type. There are narrow bands as well as wide ones. Your best bet is to take your watch in and hold it up to the different types of bands to see which one you prefer. Maybe try a watch on that already has that type of band attached. This is an item that will stay with your watch for a long period and you want to make sure you make a well considered decision.
There is a large multitude of stylish, durable watches on the market. As technology has advanced, watch makers have put their knowledge to good use. Watches of today are better put together at lower costs.
First of all, let me explain what ‘Swiss made’ means legally in this day and age. A law has been enacted regulating the ‘Swiss made’ stamp on watches and clocks. This law sets out a minimum of rules and conditions to be met before the watch can be stamped with that prestigious stamp. 
Watch bands have been with us almost since the dawn of watches that rest on our wrists. The first watch bands were made of leather and leather watchbands are with us still. Their style, width and character have changed over the years but their general shape and purpose remains the same. Certain watchbands seem to be almost timeless.