let me use chicken rice analogy here:
scenario a: I pay a large fixed sum to one chicken rice stall
and I get to eat from it anytime I want for a certain period.
But if I don't eat, still have to pay.
scenario b: I just visit any chicken rice stall when I feel like
eating chicken rice, kay chap stall when I feel like eating kway
chap etc. And if I don't eat, I don't need to pay.
scenario b offers more flexibility and variety 
v
But, but..... some chickens can have infectious diseases
leh..... 
