If you want for the long term investment i will be advice you just go for bitcoin,the price of bitcoin is low in these days so its good opportunity to buy and hold its for long time you will be get decent profit from its in future
Even bitcoin is the best cryptocurrency i think it is better to invest now with ethereum becuse the price is more affordable and a lot of newbie here im crypto can start with ethereum and for sure they can also make a huge profit with eth in the future.
Bitcoin price fluctuations are more wide than ethereum therefore bitcoin is the good coin as investment from my analysis. Ethereum as the second good investment by the way.