What's the difference ? It's the same old wine in new bottle . The speed's the same. The coaches are LHB too.
Personally speaking, in my personal opinion only. It's fine that that Railway currently is only focused on high speed bullet trains or semi high speed under 8 hours day trains. Because that's where they win from airlines.
Airlines travel will always be adding atleast a couple of extra hours for to and fro from airport, checkin and few hundred extra for the travel, whatever the destination might be in terms of domestic setting in India.
So if there's an option of say a Shatabdi with say 5-6 hours running time. People will go for that. And if we upgrade those sections to high speed, covering the same in 3-4 hours.
Bammm! We have a winning business model.
But if it's a overnight journey, and for similar expenses a person can still complete everything within 4 hours via a flight. The person will opt for it. That's why slowly Rajdhani and Duranto types will start losing significant numbers.
But we still have a very large population. For them who cannot afford , we should be looking to replace present long range journey trains with semi high speed full AC sleeper types. That's the least we can do as a nation.
And if the Railway will be honest, it will say that those section of population is not exactly their priority right now.
Bullet train is being built between Ahmedabad and Mumbai because of 2 reasons , it offers a better solution than airlines for many. And it has enough population capable enough to pay for it. Make it economically viable.
A route from Kolkata to say Varanasi will not be such. But you cannot go out in public and say that we are not building a bullet train here because you cannot pay for it, right?
Sleepers in Semi High speed trains will come. For sure. But the priority right now is DFC, Doubling/Electrification, Bullet Train and replacing shatabdi trains.
When I say Priority, I mean the only thing they are seriously working on.