One of the most important considerations is what you are planning to use the vessel for, as this will help you to choose the right boat to suit your lifestyle. To narrow down your search it is worth looking at the basic principles of hull design.
There are three main types of hull:
Displacement hulls
Displacement hulls are used for heavy vessels like trawlers and tugs. They are economic with fuel and are able to cope well with rough seas. However, they are very limited in the speeds they can reach and are better suited to long distance cruising.
Planing hulls
Planing hulls are designed to skim over the water once they have reached enough speed. They require powerful engines and are usually made of light materials to limit the weight of the vessel. They have very high fuel consumption and maintenance costs but they are very fast and a lot of fun.
Semi-displacement hulls
Semi-displacement hulls are designed to offer the best of both worlds, with both speed and practicality. They are well suited for rugged seas but are also able to reach a reasonable speed. Semi-displacement hulls are the preferred choice of hull for many designers and boat builders.