Sohna investors: Are pre-launch deals worth the gamble?

My current 2BHK in Sector 65 feels too small now, thinking of upgrading to a 3BHK or villa in Sohna. Imperialstone Infraparks in Sector 26A has some pre-launch offers. Is early-bird actually a discount, or just a psychological trick? I'm worried about getting locked in for years with no real benefit. Also, how do you guys properly evaluate super area vs carpet area? I've seen some crazy differences, worried about paying for inflated numbers. Does it really impact ROI long-term?