हमसे सीखे कोई जीने का सलीका। सफर कैसा भी हो, मौज़ उडाये जाते हैं।। - Amir

WB and Bihar are the leaders, Orissa & Jharkhand are in mid level and Assam at last.
(1)- With several intercity trains connecting the major cities with the State Capital, Almost all of the cities on railway network, large number of long distance trains WB is number one. Historically the Railway development was oriented with Kolkata as one of the 4 focal points (other being Mumbai, Chennai, Delhi). Post independence too WB got boost during the stints of Mr. Gani Khan Chowdhury & Ms Mamta Banerjee
(2) Bihar is no.2 and fairly close...
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to WB in major parameters. A lot of Rly development has taken place in last Bihar especially in last 2 decades as most of RMs hailed from this state.
(3) Orissa inherited a section of HWH-MAS & HWH-CSTM trunk lines. Substantial new lines were constructed for the mineral rich state which continues to give a huge profit to IR. After creation of ECoR zone and with efforts of state govt, many trains were introduced and substantial capacity augmentation was done.
(4) Jharkhand inherited a section of HWH-CSTM rail line. But many rail projects are progressing as Jharkhand govt participated in state's railway projects by sharing project cost. This mineral rich state too give a lot of profit to IR
(5) Assam had been a distinct laggard at the time of independence, but a lot of efforts and funds allocations have been made by IR/Govt of India to improve the connectivity of Assam to rest of the nation and the North East states through a plethora of very costly but strategically important projects (thanx to the hostile neighbouring country). Most of the lines in the state of Assam are loss making, but IR continues to spend a lot to fulfil strategic national interests.

West Bengal, without any doubt. Here are some points to suggest this:
1. There are a lot of points that can be mentioned about Howrah(HWH) station from the available options for any part of the country to facilities, the revenue generated by this station etc. Apart from HWH, SDAH and KOAA(that maintains international train) should not be ignored. Other stations in he state like NJP, Malda, Asansol, BWN, KGP etc have also got a widespread Railway connectivity.
2. Kolkata, the capital of WB is the former Indian capital, one of the six metropolitan...
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cities and most populous cities in India.The city houses some major company bases like ITC, Britannia, Bata etc. The rural area has got developed agriculture sector which is at par with the other mentioned states, at least. The presence of places like Darjeeling, the historical city of Kolkata itself etc supports tourism sector of the state.
3. Education scene of this state has got premier institutes in the picture, like IIT, ISI, IIM, Jadavpur University, IISER, NIT to name a few. The sports sector of this states is again at par with other ones with Cricket and football being most followed sports. WB hosts international cricket matches and is also important football hub of the country. There are some major steel plants and industries in the Durgapur-Asansol belt that largely supports economy of the region.
And many more!