My dilemma: choosing payment plan for Sector 24C flat

Sector 24C — been looking at flats there, kids have moved out so don't need such a big place anymore. We're selling our old house, so we'll have funds for a new compact flat. Builders often give discounts for larger down payments, but construction-linked plans feel safer. Which option is smarter if you have cash from a resale property? Worried about delays with CLP but want to save.