The best portable washer and dryer combo for apartments should have a number of features that make it convenient and easy to use. Firstly, it should be compact and lightweight so that it can be easily moved around and stored away when not in use. Secondly, it should have a high capacity so that it can accommodate a large load of laundry. Thirdly, it should have a number of different wash and dry cycles so that it can be used for different types of laundry. Finally, it should be energy efficient so that it does not add to the already high cost of living in an apartment.