.IN is far superior to .co.in, although there is room for both in the Indian growth story.
.IN is shorter and easier to quickly type, especially in a mobile centric market such as India. The .IN extension is now already thought of as the primary ccTLD for India. There are a few large corps that still use .co.in due to the fact that they had entered the Indian market a long time ago when .co.in was predominant but even those companies are now switching over to .IN
I see .IN as first choice for Indians and then if the .IN extension is not available, the .co.in option is always there as a secondary alternative. The growth rate for .IN is .INcredible right now and has no signs of slowing down, exciting times ahead indeed!