Hi i think..Rajarhat is better option. It is a very prominent location of South Kolkata. This area is gaining momentum and many residential projects coming up. Developers are offering affordable 2 and 3 bhk apartments.
Shrachi epicentre is situated in New Town AA-III while Clubtown gateway is located in Rajarhat. There are many factors which decide if the project is good to choose or not. Initially it must match your budget, the reputation of the builder, its location, how worth is the project with respect to the amenities and features provided and many more.I think you need to think about all these factors.