This choice must be made on the basis of how long you are going to invest and how long you can wait for profit. Altcoins are able to give a lot of profit in a short time, but only with a good growth of bitcoin.
BTC is the number one promising coin here in blockchain technology ,if you can afford to buy BTC it is much better here because the prices fluctuates faster and more potential to take good profits .As we notice prices of altcoin is in huge dump and we can't tell it's worth to buy in where it is risky as well ,the only one we promote is BTC.