The open button abaya as the name goes comes with buttons along the front which is a more popular option for the reasons such as being comfortable for breastfeeding so it can be flaunted for any occasion. Flexibility of styling with more than one options as mainly the movement is not restricted. The only demerit is that with time the buttons may start to loosen overtime, requiring you to sew it back also one should wear a proper pants. On the other hand the closed type is the traditional abaya which is quite simple. Wearing it quite easy as there are no buttons to open and one just need to wear it from upside. You can wear anything underneath.