Upgrading from 2BHK: Under-construction ya RTM ka tension?

Spent the whole Sunday checking out options in Vasant Kunj and Saket. Currently in a 2BHK in Sector 5 Rohini, thinking of upgrading to a 3BHK or maybe a small villa. Already have a home loan, so EMI ka tension hai. Dekh raha tha Godrej aur DLF ke projects, kuch under-construction hain, kuch RTM. Honestly, RERA horror stories sunke darr lagta hai under-construction mein. Is it worth the risk for a slightly lower price, ya RTM ka premium ab justified hai? Koi recent experience hai with these builders, especially completion delays? Aur, Delhi mein luxury segment abhi sahi investment hai ya over-priced lag raha hai?