They are designed for bright field and phase and to be used by students. This means that they have to be rugged and simple to use. Student microscopes are sold primarily to schools, no surprise there. They also make very good doctors office microscopes since they are simple, rugged and cheap. If you do not need high performance and ruggedness is very important consider a student microscope.
Dealers usually get a better price break on student microscopes.
Bench top microscopes are used in every imaginable discipline. From textiles to animal husbandry the bench top is the work horse. Bench tops can do just about any technique you can think of. The difference between a bench top and research microscope is how many techniques they can do at one time and how many documentation devices they can use at once. If this isn't a problem a bench top is a very good idea.