First-time buyer in Kondli: RTM vs UC dilemma

Been looking for 8 months now and it's getting exhausting. I'm a first-time buyer in New Delhi, focusing on Kondli. Honestly, I'm stuck between two options. One is a ready-to-move resale flat, but I'm worried about the immediate big payout for stamp duty, registration, and then interiors. Kitna extra budget karna padta hai beyond the property price? My parents keep saying resale is safer. The other option is an under-construction project by Umang Realtech, also in Kondli. It looks appealing price-wise, but delivery delays ka darr hai. Plus, hidden costs later on? Kya Umang Realtech ka track record sahi hai? Which option do you guys think is better for a first-timer like me? Need some real-world advice, please.