Greater Noida builders: long-term quality and support?

Spent the whole Sunday checking out options in Sector 150. My wife really wants a safe society for the kids, and we need at least a 3BHK. Godrej aur ATS ke projects dekhe, finishing toh achhi lag rahi thi, but baad mein construction quality ka kya haal hota hai? Gaursons se inquiry ki, response hi nahi aaya, phone bhi nahi uthaya. Booking ke baad customer support kaisa rehta hai? RERA pe kuch complaints dikhi thi for some projects, is that a big red flag? Koi experience share karega in builders ke saath, especially post-possession ka scene kaisa hai?