Slide film gives better colour contrast and depth which results in a more realistic picture. However the exposure is far more critical which can make life difficult. Also you need a way of viewing the finished material, light-box, projector or such like. Getting prints from slides is moderately expensive.

Less colour range than slides but much easier to handle. A ready to view end result.

Within slide film for example there is a wide range of different prices for different films. These like everything else have their pros and cons. I use Fuji film so I will talk in terms of their products.

Sensia 100 The cheapest in their range, can be process-paid i.e. just pop it in the envelope and it comes back developed a week later all for the price of the film. Good temperature handling, I spent three weeks in Morocco using Sensia with daytime temperatures consistently 50-60 degrees and there was no noticeable colour problems.

Provia 100 A pro version of the above, needs to be kept cool (less than 15 degrees) as much as possible but has a slightly better colour range than Sensia. I have not used it yet.

Velvia 50 Very fine grain with extremely strong colour rendition, if you glance through a book of competition winning wildlife/landscape photographs most of them are taken with Velvia. Again needs to be kept cool as much as possible.