Noida real estate: Ready-to-move or under-construction, what's your take?

15% lower rate for under-construction projects? Seems risky after all the possession delay stories. ATS Infrastructure mein invest karna sahi hai? I'm confused between ready-to-move in Sector 158 and a cheaper under-construction flat in Noida Extension. EMI and rent are almost the same, so buying makes sense. But OC milne mein kitna time lagega? What has been your experience? Should I avoid under-construction altogether? Hope to get some advice. Thanks!