I don't even believe in either of them. Although ETH's market cap has nearly caught up with Bitcoin in the past, it has never surpassed Bitcoin in its history, except for that damn Ripple coin that once beat BTC. By the way, reaching 3 million is very difficult at the moment, but it's not impossible in the future; we just need time.
If I remember correctly, XRP surpassed BTC in January 2018, and although that moment didn't last long. But think about it, even a lousy coin like XRP could surpass BTC in capitalization in 2018, the scenario of ETH surpassing BTC is much more feasible than bitcoin reaching $3 million.
As for bitcoin hitting $3 million, I won't believe it and won't rush to think about it until bitcoin hits $1 million. Bitcoin is even further away from the 1 million target and no one knows when that will happen, let alone the 3 million target, that's too vague.