I like ARKK a bit more because it's more diversified and also covers some of the top holdings in all the other ARK ETFs including ARKG, whereas ARKG feels a bit riskier since it covers a relatively narrow sector.

That said, just over half of my entire portfolio is in ARKK/ARKG, while the other slightly less than half is in VOO/QQQ. But I tend to be relatively risk-tolerant and am okay with some volatility rather than going too heavily into index funds. My reasoning is that even if the ARK funds are riskier than index funds, in the end, they're still ETFs split amongst around 50 companies each -- even if Tesla theoretically went to $0, it's "only" 10% of ARKK.