In your mind, which platform will have more transactions and therefore secure in the future.
With transactions it's undeniably ethereum but for security in the future, can you describe more of what type of security is this?
Secured in a way that many are using it or it's entire networks security?
Keep in mind that Ethereum starts 3 years ago while Bitcoin starts 9 years ago. Also consider the fact that Ethereum can handle more transaction per second than bitcoin.
So what if Ethereum started 3 years ago? it's network can be also congested same as bitcoin.