Watch straps are made from many different materials. What material you decide you like for a watch strap will largely depend on what feels the most comfortable for you.
Watch straps made from leather are quite comfortable, sturdy and stylish. The downside is that if they absorb a lot of sweat or dampness in general, they can start to smell bad. You can counteract this by keeping them as dry as possible and cleaning them once in a while (making sure to thoroughly dry them afterward).
Rubber or Polyurethane
Rubber and polyurethane straps are usually inexpensive and can be quite sturdy. Some people have found that they encourage sweating if they are worn tight to the wrist but if worn slightly loose this allows air flow under the watch, which cuts down on the sweating. They are also easy to clean if they happen to get dirty. Rubber bands can also have a distinctive rubber smell to them, which some people don’t like. While other types of bands may last for years, rubber and polyurethane bands will need to be replaced every six to 18 months.
Nylon bands are generally touted as being inexpensive, extremely comfortable and easy to wash, as they can be put in a dishwasher or washing machine. They are the most breathable of the different types of watch straps but can also get dirty quite easily. Because nylon straps go over each spring bar and under the watch back, both spring bars would need to fail for the watch to fall off, whereas with other straps, only one spring bar failing would result in the watch falling off and possibly being damaged or lost. The nylon strap can get torn and fray and these straps will likely need to be replaced every six to 18 months.
While metal bracelets are generally quite sturdy, they are also made up of several small pieces, including small pins so they may not be quite as sturdy as they look. Because they are made from several small pieces, they can sometimes pull arm hair or pinch the skin, although this isn’t always the case. Designs have evolved to limit this from happening. Obviously metal bracelets are heavier than other types of straps and tend to get scratched and dinged up from use. A good metal strap may very well last the lifetime of the watch. They are more expensive than other types of watch bands.
Ultimately, the different types of watch strap you decide on will depend on what you find most comfortable. You may find that it is a good idea to have a few different straps for different occasions or seasons. Also keep in mind that for any strap, the sturdiness is highly dependent on the spring bar, as this is where most failures occur.