There are plenty of options to choose from, and without knowing your preference for fuel, gearbox, and rear space its a bit hard to pinpoint. However, the Maruti Suzuki Fronx would be a good all-rounder. With your budget, you would get the top trims and thus enjoy more features. 

The Fronx is also fairly easy to drive with a compact sub-4-meter length, light enough controls and a slightly elevated seating position that will give you a better view outside. 

Moreover, its taller stance offers you a good ground clearance handy for your occasional weekend trips outside the city. As for space rear room is good, as is the boot space too, so for your family of 4, this should do just fine.     

The Tata Sierra is clearly the larger of the two cars and will give you more space than the Maruti Fronx, as well as a better ride, too. However, the base version of the Sierra isn't as well-equipped as the Fronx. 

More importantly for you, the versions that fit your budget come with the 1.5-litre naturally aspirated engine, which is quite weak in its power delivery and not ideal for you, given that you are mostly driving on highways. Thus, a high variant of the Fronx would suit you better.    

If you are a new driver, choosing an automatic transmission will be comfortable and convenient for city driving. Since most of your usage is in urban conditions, you can choose either Maruti Suzuki Fronx Alpha AT or the Hyundai Venue HX6 DCT. 

Both are reliable and easy to maintain. Fronx makes more sense if you plan to move to a tier-2 or tier-3 city. Maruti Suzuki has the widest service network and easy availability of spare parts, which adds to long-term peace of mind.

The Nissan Magnite CNG is available with a 1.0-litre naturally aspirated petrol engine, which is barely adequate to power this car. Furthermore, while running on CNG, performance will be lacklustre, and efficiency will also be low. And as you mentioned, resale value will be poor, hence it is best that you look at other options.

The Maruti Suzuki Fronx gets all the basic safety features like ABS with EBD and ESP, which prevent an accident from happening in the first place. Additionally, there are 6 airbags to keep you protected in case of an impact. Do note that the Fronx's petrol engine is much smoother, and overall, it is much nicer to drive. 

However, if you want a proven, safe CNG car, go for the Tata Punch or Tata Altroz. While their powertrain isn't as smooth or as good as Maruti's, these are practical and spacious alternatives.

If you want efficiency, the Kia Sonet diesel is the one to go for. Beyond the cost advantage of running a diesel, the Sonet diesel is actually nicer to drive than the Maruti-Suzuki Fronx petrol. 

The Sonet 1.5 diesel offers better performance and works well with the 6-speed automatic transmission. The Fronx is, of course, cheaper, but if you have the budget and want a car with low running costs and want an alternative to petrol, then the Sonet diesel is for you. 
 

• Hatchback: Maruti Suzuki Swift
• Compact sedan: Honda Amaze, Maruti Suzuki Dzire
• Compact SUV/Crossover: Maruti Suzuki Fronx, Maruti Suzuki Brezza, Hyundai Exter

The Hyundai Venue Turbo DCT is a good package, but it is on the pricey side by segment standards. 

The HX5 variant does get reasonable features, but we would urge you to consider the HX6 version. While the price gap from the HX5 to HX6 is significant, the HX6 does get essential safety features like a rear wiper, adjustable rear headrests and wider tyres. Of course, the jump to HX6 also brings in more comfort features such as a rear armrest and auto climate control, among others.   

Alternatively, you could consider the Kia Sonet Turbo DCT HTX, Mahindra XUV 3XO AX5 and Maruti Suzuki Fronx Turbo Zeta, all of which offer good automatic gearboxes. Also pack in plenty of comfort and safety features within your Rs 13 lakh budget.