Altcoins itself is a group of coins so what particular coin are you preferring too? Bitcoins on the other hand was considered are the most successful investment in this period of time and it has bwwn said by the mainstream news so a lot of people are gonna kmow it so it is much reliable than altcoins and besides the image of altcoins had been ruined because of those plenty shitcoins and scams that people always encounter that is why they have trust issues om altcoins rather than bitcoins. So for me bitcoins is the most reliable and altcoins on the other hand have omly few reliable coins like ethereum and waves.