Trees also tend to grow in different shapes. Some grow kind of straight up in what is called a fastigate shape. They can also be cone shaped such as the fir tree or weeping such as the weeping willow. Each shape has its advantages. Consider what you want the tree to do for your landscaping and choose accordingly.
Trees also vary in growth rate.
Just as you would consider growth with a shrub, think about how large the tree may get. You may want privacy as soon as possible but consider that the tree may reach a height that no longer provides privacy but just shades your house. Many people may choose to start with a fast growing specimen and then move it in a year or two when it becomes too large for the original chosen spot. They will often plant this tree next to a more slow growing variety so that when they are ready to move the fast growing tree there is another tree just the right size and shape to take up the job of shielding the house from unwelcome sightseers. Vines Vines and climbers can be very fast growing inexpensive alternative to putting up a solid wall.