Ambika Realcon pre-launch: Construction-linked payment plan better for investors?

Did a site visit to Ambika Realcon in Sector 18D last weekend. They're offering a pre-launch for a 3BHK, price around ₹1.5 Cr. Builder bol raha hai ki early-bird discount mil raha hai. But I'm confused about the payment plans – they have construction-linked and a 20:80 scheme. Should I go for the down payment heavy one for better negotiation, or is construction-linked safer for an investor? Parents kehte hain ki pre-launch mein hidden costs zyada hote hain. Kya builders actually give good discounts during pre-launch, ya bas hype hai? Kitna leverage milta hai payment plan se?