The biggest attribute of Subway is that their sandwiches are inexpensive and filling. The negative is that the sandwiches have a great deal of bread to fill you up.
The next big attribute is that they are fast. Most of the time you can walk in and 5 minutes later have your big sandwich and drink with you. There is little room to sit and eat, almost everyone leaves with their food.
The sandwich makings come in many varieties of bread, many varieties of meat, many varieties of garnishes and sauces. There must be 10,000 different combinations of food, all available instantly.
The sevice is also friendly and good.