There are two issues. One is which coin will be used as a store of value, like gold. Bitcoin is way ahead here and I think it will stay ahead.
The second is which coin will be used as a currency, to buy and sell stuff. Here the jury is out: the blocksize issue, the length of time it takes for transactions to confirm, the fees for sending, all these thngs mean that bitcoin is not likely to be used as a currency any time soon. But if not bitcoin which alt? The only coin that has a rising number of transactions per 24 hours is Ether.
Point is that none of these aspects, namely "store of value in the long term", or "currency to buy and sell stuff" is what is driving the crypto currency market BY FAR. Almost all people who are in crypto currency (bitcoin and alt coins) are into the speculative aspect of "wanting to gain value" with it. True, some are into this for the shorter term (wanting gains on volatility, day traders) ; others are in the longer term into it (hodlers), but almost all of them are in it for (hopefully LARGE) gains.
A small minority of people are into crypto to buy stuff with it ; dark markets are the main application, and bitcoin is still (despite its transparent chain) mostly used there. And yes, a few geeks like to buy stuff legally on the internet with bitcoin (me too).
Another small minority of people are really into crypto, and mostly, bitcoin, to hedge against the potential woos of the financial system.
But, by far, most users are in it for BIG PROFITS (in the short or long term). This is what keeps the exchanges going, this is what determines market cap, and this is what determines volume. ==> it are speculative assets to gamble on.
Now, speculative assets derive their "value" (that is to say, their hoped-for potential to make you rich) from the amount of greater fools that flow in (long term hodling and dream of moon) ; or the amount of fellow traders that play, just as you are, on the volatility.
It is true that, concerning volatility, alt coins are superior to bitcoin since a while ; but it is also true that the bigger the existing pyramid is (the higher the given market cap of a coin), the smaller the hope is to find a lot more of greater fools. At that point, it becomes interesting to look at smaller pyramids with larger growth potential - even though the big pyramids are still attractive and feel somewhat safer.
I guess the recent shift of inflowing capital from bitcoin to dominantly alt coins, reflects this: smaller pyramids have higher potential growth in greater fool games than already very big pyramids, but the big pyramids are still filling in big layers of newcomers at high prices.