Many people invest in both VOO and QM at the same time, thinking that this diversifies their risk.

In reality, you are just buying the same companies—NVIDIA, Apple, Microsoft, etc.—twice.
VOO tracks the S&P 500, while QM tracks the Nasdaq 100. The overlap in the top ten holdings is over half, with core companies like NVIDIA, Apple, Microsoft, Amazon, and Broadcom ranking high in both.
Many people think that adding QM increases their AI exposure. In fact, you are just adding more of the same batch of companies, only with a more concentrated position.
The real difference between the two is not what they hold, but how much they hold.
The weight of the technology sector in VOO is around 33%, while in QM it is close to 60%.
Take Micron as an example: its weight in QM is nearly 4.8%, but among VOO's 500 constituents, its weight is less than 2%; the same goes for AMD.
So, dollar-cost averaging into both VOO and QM at the same time is not inherently a problem.
What really needs to be considered is the allocation ratio.
If your goal is simply to achieve long-term returns from U.S. stocks, VOO is already sufficient.
If you are bullish on the AI cycle and hope for higher returns, you should appropriately increase the proportion of QM, rather than thinking that buying two ETFs will simultaneously achieve diversification and concentrated betting.