What exactly are you looking for in the car? That would help narrow the choice down. If you are going to be using the rear seats a lot, and need a spacious car for 4 people or at the most 5 with good fuel economy, then the Sunny diesel is a good choice. However, if you want a car that is powerful, and great to drive, with a touch of class, the Vento feels a lot more plush. The Ertiga should be considered only if you really need to carry 7 people once in a way or need that flexibility of space, and as long as you don't mind the MPV look.

I'm taking the Vento out of the equation for you as it stands nowhere in terms of space when compared to the Sunny and Ertiga. That said both the Ertiga and the Sunny are spacious and comfortable vehicles. Here the choice depends on whether you need the extra row of seats in the Ertiga. Also they are two separate segments and the Sunny looks more elegant and classy. On the flip side the Ertiga has an attractive price for an MPV and is a Maruti, so there is ease of serviceability :) The Sunny although a great car is a Nissan, so service and spares will cost you more. If your nearest service center and dealer are close to you house then you can safely buy the Sunny.

Classiest is the Vento. Most spacious is the Ertiga as it can carry 7 people when needed. If you dont need a 7-seater, then choose between vento (classy) and Sunny (spacious). If you need the extra two seats, it is Ertiga definitely. The most value for money according to me is the ertiga.

It is a fact that many car companies are making a killing in the name of service and maintenance at the expense of the customer. Leading the pack in no particular order are Skoda, VW and Mahindra. That being said, go ahead with the Sunny. Its a decent car for the city and very spacious too. Drivability and FE are excellent with minimal turbo lag. And you being a Delhite will not have to worry about Nissan's limited number of dealers.