Get the 2GB one, the extra VRAM will come handy in future titles, especially with the new consoles coming out textures will get more heavy. The 650ti is no slouch it is comparable to the 560 non ti. I feel it will be able to utilize the extra 1GB especially with some overclock. Even with Crysis 3 2GB Cards are recommended. Its only 1k more. If you use the card for 2 years, its like Rs40 a month more.
Just a query to everyone here, wont the OP benefit from an AMD card? Since the new consoles are based on AMD APUs which outperform the Nvidia cards in compute performance, newer games will be utilizing compute. Maybe not this year but next year onwards?