Noida investment: Sector 3 or Noida Extension?

Looking to invest in Noida, but confused between Sector 3 and Noida Extension. Sector 3 seems established, but Noida Extension has more new projects. What do you think? Which one is better for long-term appreciation? Also, has anyone invested with NS Promoters? Their projects look good, but I'm not sure about their track record. Kya aap logon ko pata hai about rental yield in these areas? I'm hoping for decent returns. Mujhe advice chahiye on whether to go for under-construction or ready-to-move. What's your take? Is it worth the risk of construction delays in Noida Extension? Any suggestions?