The amount of vitamins and minerals can be easily increased or decreased by taking more or fewer of the multiple. Most multiples have all the ingredients mixed together. Sometimes the B vitamins react with the rest of the ingredients in the capsule or tablet. This reaction is sped up in the presence of moisture or heat. While the multiple is still safe and effective, the smell is off-putting and usually not very well tolerated.
Some people find capsules easier to swallow.
This is often a function of size. Capsules are usually not as large as a tablet. Some people prefer vegetarian multiples. While some capsules are made from vegetarian sources, most come from animal gelatin. Vegetarians need to carefully read the label to ensure they are getting a vegetarian product.