I don't know about south indian. In Hong Kong, i guess most people use a rice cooker to cook rice. we could use a metallic pot or clay pot to cook rice. i heard that clay pot can conduct better heat and make every rice cook evenly. For most rice, use a 1:1 or 1.5 ratio of 1 cup of rice to 1.5 cup of water . the ratio can be varied from how soft or chewy the rice you want it to be. For the portion, a half cup of uncooked rice is good for 1 person. 

Thanks Eric for your response. I am interested to know the recipe used in the states of Tamil Nadu and Kerala of India, who I know use parboiled rice.

Hi- 

Both are used from what my experiences have been with the community, predominantly south asian. The rice cooker is used as it is convenient, and keeps the rice warm. Some households still use the straining method, perhaps when cooking for large groups, making biryani, in which case the Rice can be baked in a source of liquid.

Thanks Thevaki for your response. I am not sure if you have reported your observations in the Immigrants in Canada. In Bangladesh, almost all households whose staple is parboiled rice and cook in a traditional pot on an open flame use an abundant amount of water, then decant or strain (usually when cook large amounts e.g. for a festival) the excess water when rice is done. I am keen to know this is the common practice in southern India.