Since this is the most frequently asked question, I have decided to answer it, even though I have only personally tested three purifiers so far.

http://www.saurabhja.in/which-purifier-should-you-buy/

There is also an FAQ section now. Please, please ask questions. I've received some excellent questions over WhatsApp and I will be including those here later in the day.

http://www.saurabhja.in/category/pollution/faq/