Gurugram 3BHK: Pre-launch and payment plan catches

Is pre-launch pricing for Gurugram projects actually a better deal than ready ones? Builder bolte hain discount milta hai, but payment plan mein interest cost bhi toh add hota hai. For a 3BHK in Sector 83, should I consider construction-linked plans or wait for completion? What hidden catches should I look out for as an end-user? Koi actual savings hui hai kisi ki?