It is normal to think that it is better to have two cookers, one with smaller size. It is indeed useful when you want to cook smaller things like dhal or rice for one person or just as a standby. However, please beware of its associated danger.
These small cookers are as good as mini explosives. I still feel the chill in my spine when I recall the way it choked once while my wife was cooking rice in it.
It simply clogged the vent and without knowing it, she was trying to open the cooker. Since prestige and other such brands offer outer lids, there is no safety against such dangers. For example, Hawkins cooker comes with inner lid and hence, you can not open the lid if the pressure inside it is not yet equilibrated.
Fortunately I sensed the danger and stopped my wife from opening the lid. Please take care friends... it may lead your home into a hell.