If you prefer long term you should try bitcoin and etherium. But if you prefer short term you should try altcoins. It depends on you, if you prefer fast earnings go short term and try altcoins. But if you prefer more big earnings but takes a long period of time go long term and try bitcoin. Its both good because these coins are profitable.
It's not only bitcoin and ETH which will succeed, I think we also have to consider other coins or tokens, as long as they have solid
future plan they'll be able to get a support. Invest on strong coins but also do not miss-look coins which are undervalued but have a good future potential.