The Mahindra XUV700 is a reliable and well-packaged SUV that is strong on road presence, has a good amount of equipment and a strong set of powertrains. Both, the petrol and diesel engines are strong, and while the diesel is more efficient, check if your annual mileage is above 15-20,000km. The Tata Harrier/Safari have a stronger road presence but are not as reliable or efficient as the Mahindra. 

In the ₹30 lakh budget, the three best options for you are the Jeep Compass, Tata Harrier, and Mahindra XUV700. Each of these SUVs is very capable and has its own set of strengths, including your main requirement of good and stable ride comfort

However, we would recommend the Mahindra XUV700. It offers multiple engine and gearbox options, including optional AWD for better control. 

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.  

If most of your driving is in town and the third row will only be used occasionally, the Hyundai Alcazar is a better fit. The 116hp, 1.5-litre diesel engine isn’t very punchy, but the Alcazar’s light controls and compact dimensions make it friendlier to drive on congested roads. It also comes absolutely loaded with features and offers a 160hp, 1.5-litre turbo-petrol option.

However, if you do frequent road trips with your family or spend a lot of time on highways, the Tata Safari is the better choice. The Safari has a far more usable third row, and the 170hp, 2.0-litre diesel engine can comfortably haul six or seven passengers. It also feels tougher overall.

As for the Safari petrol, that option will take some time. Tata plans to debut its new 1.5-litre turbo-petrol engine in the Sierra SUV first, which will later be introduced in other Tata models, including the Safari and Harrier.