Why should I NOT buy the ETF vs BTC?

I have a good amount of btc already, but just holding it in my cold wallet and exchange makes me nervous somewhat. I see all the benefits of the upcoming ETF such a being able to hold in tax advantaged accounts or not having to get hacked/lose btc. Because of this, I’m leaning towards directing most of my btc spending on the ETF.

Are there any disadvantages to buying the ETF over BTC? Does the price of the ETF directly correlate with the price of BTC? anything else I should be considering?