9 MG cars in India

Since your intended usage will be in Kolkata traffic, we don't recommend a diesel engine, like you have in your other two cars. Depending on your budget, you could consider a petrol car or even an EV. Among petrol cars, you could get a Maruti Swift under Rs 10 lakh, which is easygoing and efficient. And if you're after an EV, consider the MG Comet EV if you don't need a lot of space - its compact footprint makes it ideal for traffic. An EV will always have lower running costs and a smoother drive than a petrol car, which is helpful in traffic.

Since your running is 500km a month and within city limits, an EV makes sense for you. However, given your budget is around Rs 10 lakh, both the MG Windsor EV and Tata Nexon EV are more expensive than that. Alternatively, you should consider the Tata Punch EV. 

The ARAI claimed Tata Punch EV range is 265 km for the smaller 25 kWh battery pack version and 365 km for the larger 35 kWh long range (LR) version, with a real-world LR range of around 229 km. Power and torque outputs are 82hp and 114 Nm for Standard and 122 hp and 190 Nm for Long Range. The Punch EV is ideal for urban users who want a compact, well-equipped EV with solid performance and comfort. Tata Punch EV prices start at Rs 9.99 lakh and go up to Rs 14.44 lakh (ex-showroom). 

If you are open to buying an electric vehicle, the Tata Tiago EV is a good option for city use. It's got a smooth powertrain and is much more practical than the MG Comet you also considered. There's also the option of the Tata Punch EV, though it is slightly out of your budget. 

Among petrol automatic cars within your budget, the Hyundai i20 iVT and Citroen C3 AT have the smoothest automatic gearboxes. The Maruti Suzuki Swift AMT is also a good city car, though the AMT gearbox isn't as nice. 
 

The Tata Punch EV is a really well-rounded vehicle, and makes for a great EV runabout. However, if you are open to its unconventional styling and two-door layout, the MG Comet is an excellent secondary vehicle on account of its compact dimensions. It is very easy to drive and park, and it is one of those cars which you will truly appreciate for its merits as you begin to live with it.

Given your requirement for good rear seat comfort, you could consider the MG Hector. It is a spacious SUV and scores well on rear seat comfort. However, fuel economy on the petrol version is poor. 
Other options worth looking at include the Mahindra XUV700, Tata Harrier, Hyundai Creta and Kia Seltos.