Rockfort Express: திருச்சி அவனது கோட்டை, இரவில் சென்னை வரை வேட்டை, அவன் தான் மலைக்கோட்டை. - Vijay Baradwaj

bhai technology isn't like characters in hindi serials i.e. Either black (evil) or white (saint-like). Depending on where and how you want to use each will have its own advantages. Sturdiness for example has never been the forte for electronic devices, while low maintenance isn't something you associate with DC motor. you have to consider which of the availablee technology is good and suits your need, which is why component engineer exist.
As for your declaration, i take no responsibility for you being bevakoof :p

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Jo superfast WAP4 pe chal rhi hai, jab unko WAP7 milega tab unka WAP4 passenger aur express ko mil jaega

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Ab short distance train o ko memu/demu me convert kiya jaa raha hai

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There are a lot of mail express which may get WAP4

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P:-4 to abhi bhi milta bahut saari train o ko unka link upgrade hoga p7 se

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