Noida property search: delivery delays or construction quality?

My kids' school admission depends on this, so I need to decide fast. Was supposed to buy resale in Sector 75, but my wife's priority is a new 3BHK. Looked at Mahagun, but heard about delays. Honestly not sure if it's worth the risk, even if the location is perfect. Saw some flats by ATS. Their construction seemed solid, but someone mentioned hidden charges popping up at possession. Is that true? Need at least a 3BHK that's safe for the children. Anyone had good or bad experiences with possession from these builders? Which one is more reliable in terms of on-time delivery and no surprises at handover?