I would not buy just one coin. It is safer and more profitable to buy some of the best coins. You can see the cryptocurrency statistics and buy the top 10 coins, so you distribute the risks
if I only compare IOTA with bitcoin head to head, of course I will choose bitcoin and many people will think the same as me. bitcoin is the top marketcaps, that means the user is the biggest, has a large community, etc. that is important in safely investment