Go for full HD smart TV.
You can watch HD content on HD channels and on youtube also.
Smart TV can provide internet based apps and Wi-fi connectivity in home network.
Though 4k is still far away because of high price of 4k tvs and low availability of 4k content Full HD TV is must these days.
Future of watching TV is in VOD apps like Netflix, Bigflix, Voot, Sony Liv and Jio Play/Jio onDemand.
Wi-fi connectivity is also useful to play content directly from your mobile and PC.
Last week I purchased Sony Bravia W592D full HD smart TV in Rs. 33000/- for my brother. You can consider this model.