The basic version of Tata Nano will cost you more than Rs. 1,60,000 (On Road Bangalore), which is almost 1 lakh more than what you are giving for 800. But still I would like to be the first owner of Tata Nano, but not the second owner of Maruti 800(96000 Km driven 10 year old). I agree Maruti car's parts are easily available and cheap but still I would'nt like to visit service center or garage every now and then.
If you can stretch your budget Tata Nano is recommended.