You may not notice it in 4R prints these days due to the advances in film manufacturing which has resulted in very fine grain ISO 400 film. Always use slow film if you are able to use a tripod. In such a case whereby you need to hand-hold the camera, get a faster speed, but the rule of thumb is always get the slowest that you can possibly manage. This is simply a matter of choice, personal taste, or necessity. Some prefer the richness of slides, whilst others want the convenience of sharing photographs through prints.
Some photographers even use infrared film to get special effects.
Again, this is up to the photographer. Or, you may wish to capture the richness of the sunset or the multi-coloured neon lights of the city. Tungsten film, as it is commonly called, is usually labelled with a T in the film name. This is beyond the scope of this article. If you are using a tripod, there is no worry as to how fast or slow your shutter speed should be.