As far as I know (according to my friends), the best hostel is Meenakshi. The rooms are better furnished, with attached bathrooms, bigger size and is air-conditioned. The food is also far better than the food that they serve in the normal girls hostel since the food at Meenakshi comes from SRM Hotel.
Other perks include proximity to the main gate, close by stationary shops and a restaurant, proximity to the University Building (Central Library), etc.