Under-construction: The hidden costs of waiting in Sohna

My landlord just hiked the rent again, I'm so fed up of renting. Finally decided to buy something in Sohna. Dekh raha hoon options around Golf Course Extension Road, but confused between under-construction and ready-to-move. RERA ke baad bhi bahut delays sunne ko milte hain. Like, if I consider a Godrej or M3M 3BHK for ₹1.5 Cr, is waiting 3-4 saal worth it? Or should I pay more for RTM? Builder ka track record kitna important hai, ya koi aur red flags bhi hote hain?