Ready to move is always better, change my mind

Okay I'll be honest – I'm totally confused about under-construction vs ready-to-move. Kids have moved out, and we're selling our big house. Want something manageable in Noida, maybe Sector 108. Has anyone had a good experience with Cosy Reality projects? Seen some ready-to-move flats, but the under-construction ones are cheaper. But phir, RERA horror stories... don't want to get stuck. Resale of our existing property is key. I'm also wondering about the rental yield reality. Are those advertised numbers actually achievable or total bakwas? Should I just stick to ready-to-move for peace of mind? Is it worth paying extra to avoid the headache?