What nobody tells you about pre-launch discounts

Pre-launch pricing for Keya Homes near Nayandahalli feels like a big gamble. I'm eyeing a 2BHK there. Is the 'early bird discount' actually worth the risk, or just marketing? What's the real appreciation difference between a 2BHK and 3BHK in these Bengaluru projects? Wondering if I should just wait for ready-to-move.