This is a great link about about map projections and how they differ. Depending on what I want to use a map for would depend on what type of projection I would use.

There are five things that are affected by what projection is used for a map. They are:

1. Conformality (the appearance or shape)
2. Distance
3. Direction
4. Scale
5. Area

Each projection will preserve one of more of the above attributes while degrading the remaining attributes.

This is why Greenland always looks so huge on most world maps. If you were concerned about the actual size and shape of Greenland, you would select a different projection, and make sure that the projection intersects Greenland.