Fidelity's "Zero" funds are great, but only for specific scenarios IMO. They can't be held outside Fidelity accounts, so what happens if you get caught up in some KYC nonsense and Fidelity closes your account? Are you forced to liquidate and incur capital gains? There are also some embedded tax efficiencies inherent to ETFs, like 351 exchanges, which aren't popular now, but may become popular in the future. TBH, this mainly applies to taxable accounts. For nontaxable accounts, Zero funds don't have much downside.