They are two different propositions. Ethereum has more long term potential. When I say long term I'm talking 5 to 10 years. Dont worry bitcoin is not going to disappear any time soon.
yes bitcoin even has more potential, because the price of bitcoin already cross 2000 USD level and still going to increase. people are are still very confident about bitcoin they are even not going to sell their bitcoin and going to keep them for next high price.
in fact bitcoin is the main currency that people use not only for trading and investment but they also use it for so many other purposes. as we most use bitcoin for online shopping, because most of the online shops only accept bitcoin for shopping and not any other currency.