All of you might have seen that low capacity refrigerators are generally single door. As the capacity increases, no. of doors increases. In any case, no. of door add extra cost. More the no. of door, more convenient to store the food. Because if you want to store vegetable at lower end of refrigerator, simply open that door and put that. It is bound to save energy also. For security also, more doors are beneficial. If you want to prohibit some people (say kids) to get some particular thing from machine, lock that door only.
Summarily, do cost vs benefit analysis and purchase the best suited machine.