Sail U-VA is a good car, it is spacious, interior quality is good and it derive its power from Fiat sourced 1.3-litre Multi-jet engine, which is the same engine, which does duty in Maruti Suzuki Swift. The car comes with all important features and cost lesser, additionally Chevrolet offers 5 year warranty on engine and transmission and offers 3 year Chevrolet promise of cashless maintenance.
It is great that you wish to buy a new car and we are happy to be a part of your new car purchase. The cars that you have selected compete neck to neck. Brezza is a "Maruti" that means you get least maintenance, more mileage and better resale value, technically it is more economic. However, it misses out on power, looks and built quality. Ecosport on the other hand has got enourmous amount of power, has got better built quality but misses out on mileage and maintenance. Thus, if you are looking for a car which is readily available, you should choose EcoSport as Brezza has a huge waiting period and if you wish to buy something which is more "Economic or pocket friendly" go for Brezza. Click here to check out the comparison.
Hey, it is great that you wish to buy a new car, we assure you that Polo does not offer 6 airbags in any of the variant. Talking about cars which offer them in the budget of 8 lakhs. It is just Figo Aspire which offers 6 airbags apart from the names that you've mentioned. In the competition you have Baleno and Jazz which do not feature 6 airbags.