I think neither of them is the future tbh and a combination of strong altcoins (different coins for different use cases and or features) will be the future.
Other coins are still dependent on bitcoin/eth etc as an intermediary exchange value, once it becomes easier to convert altcoins to usd (a lot of projects are working on automatic exchanges etc) then there is no reason that a newer coin with a better technical implementation becomes the new standard for a certain use case or feature. Of course it will take some time for that to happen.
Lol good luck with the sea of altcoins that overpromise way too much and underdeliver by a huge amounts. People forget how difficult building the actual technology is. Writing a whitepaper isn't how you build things. Bitcoin has survived in the wild for a long time. Ethereum has its own strengths although less proven adversarially than Bitcoin. A sea of altcoins with shiny whitepapers are not going to replace them.