Mohali investors: Is pre-launch truly better than resale?

Honestly, I'm realizing how much I don't know about timing the market. Currently in a 2BHK in Sector 51, looking to upgrade to a 3BHK. Builders like Action Constructwell push pre-launch schemes. Is that truly a discount, or do secondary market deals offer more value for a 3BHK around ₹2 Cr? Can we negotiate better in resale?