When choosing a microscope the most important factor is what kind of samples/objects do you intend to observe. What you need to see and what you want to do with that image will determine what kind of microscope you need, there are many different types of microscopes, and no single microscope can view everything. You also need to take into consideration what sort of magnification or resolution are you looking for. What kind of light will you need in the microscope. What type of contrast do you plan on using. What is the consistency of the sample.
Two most common types are compound and stereo microscopes. Common offers a high magnification with two dimensional images and is better for samples such as cells. Stereo offers a three dimensional image and is better used on larger objects such as circuit boards. Stereo also uses completely independent paths of light. and uses two different angles of viewing to create an impression of depth and solidity.