Some of the most common critiques of Bitcoin are: "it's too slow" or "the blockchain is getting too big". Sure newer coins offer faster tech, more sophisticated algorithms that are ASIC resistant, and so on. Let me ask you this - do you ever ride the old train in your city? Do you sit on the train and wonder why they don't put in a new superconducting train instead? We use the old train and it's no wonder because it works. Don't fix something that isn't broken, haven't we all learned that the hard way? And if it breaks down, surely it will be cheap to repair. Besides, what do you think cost more to complete, the train itself or clearing the path and laying the tracks? Bitcoin has value because it is a store of currency that will appreciate AND because it's just there. How can you buy the hottest new altcoin? Directly with fiat? You must but BTC from a Bitcoin exchange, then trade it on an altcoin exchange.
So often I see people saying "we are in a bubble" and "when the bubble bursts..." - but weren't these people saying the same thing when BTC made a huge push up to 2,700? Maybe we simply underestimated Bitcoin. Remember, Bitcoin is the first of its kind. We can't really look to history to predict how it will be valued like we can with other things.
So before you sell your coins, ask yourself this: how long has the old train been running in your city?
Your train analogy is completely inapposite. There are old trains which still live today, but only for tourism purpose. If you need to use a train to go somewhere, like your office or your school, surely you don't want to waste time on an old train, but you'll catch the fastest modern one.
Also, some exchanges allow to buy altcoins directly using USD or EUR, so you don't need to use Bitcoin.
