Cathie Wood is the CEO and founder of Ark Invest, an asset management company focused on disruptive technologies like DNA sequencing, blockchain, and robotics. But few technologies have as much disruptive potential as robotaxis. Ark believes autonomous ride-hailing platforms could generate $4 trillion in revenue by 2027 and $9 trillion in revenue by 2030.

Here are two growth stocks that should benefit from that tailwind.

1. Tesla

Tesla (TSLA 1.52%) once again led the industry in battery electric vehicle (BEV) sales in the first quarter, capturing 24% market share. Tesla also achieved the highest operating margin among volume automakers last year, something CEO Elon Musk attributes to unparalleled manufacturing technology. More importantly, management believes deliveries will increase at 50% annually over the long term, and CFO Zach Kirkhorn believes the company will retain its industry-leading margins in the future.

One reason for that confidence is the new vehicle assembly system Tesla plans to debut at Gigafactory Mexico in 2024. The system promises to cut production costs in half and reduce its factory footprint by 40%. Management also believes full self-driving (FSD) software will be an important source of profitability in the future. FSD software can be sold at 100% gross profit, and it will power the robotaxis Tesla plans to mass produce in 2024.

After adding a robotaxi to its arsenal, Tesla will likely launch an autonomous ride-hailing service, and investors have good reason to think the company will be successful. Musk says Tesla is one of the world's foremost artificial intelligence (AI) companies due to its expertise in software and hardware. Tesla has more autopilot-enabled vehicles on the road than its peers, meaning it has more autonomous driving data than any other automaker. That gives the company an edge because data is the backbone of AI. Additionally, Musk says the supercomputer that powers its FSD platform is the "most efficient inference computer in the world."

Here's the bottom line: Tesla has a strong competitive position in the BEV market, and the company is arguably a leader in autonomous driving technology. That positions Tesla for strong growth in the coming years, and its currently valuation of 10 times sales -- a discount to the three-year average of 16 times sales -- looks reasonable in that context. However, Tesla still trades at an outrageously expensive valuation compared to other automakers, indicating that Wall Street has big expectations. Investors that believe in the robotaxi narrative should buy a small position in this growth stock today, but investors that lack confidence in that narrative should steer clear of Tesla.

2. Alphabet

Alphabet (GOOG 0.80%) (GOOGL 0.86%) is best known as the parent company of Google, but it owns several other subsidiaries that could one day contribute to the overall financial picture. Autonomous driving technology company Waymo is one of those subsidiaries, and the business can be broken into two divisions: Waymo One provides commercial ride-hailing services, and Waymo Via provides autonomous trucking and logistics services.

In 2018, Waymo One became the first commercial autonomous ride-hailing service when it launched in Phoenix. Today, anyone in Metro Phoenix can download the mobile app and request a robotaxi. The company has also expanded into parts of San Francisco and it plans to enter Los Angeles in the near future. Consultancy Guidehouse recently recognized Waymo as the second best autonomous driving technology company behind Mobileye, though Ark would undoubtedly put Tesla on top.

Alphabet and Tesla have different strategies when it comes to autonomous vehicles, and they have frequently traded criticisms. Tesla relies entirely on computer vision. That approach is more complicated but it offers a bigger potential payoff. Once perfected, Tesla's FSD software will theoretically be able to navigate any road in the world, even those it has never seen.

Meanwhile, Waymo leans heavily on lidar, a technology that uses lasers to measure the distance between objects. Its vehicles are essentially on rails because they can only operate on roads that have been pre-mapped in meticulous detail. That means Waymo will have to grow city by city, mapping every centimeter of road in each new location. But the upside to that less complicated approach is that Waymo beat Tesla to the punch; it already has an operational autonomous ride-hailing service.

Investors should also consider the big picture. Alphabet could be a great investment even if Waymo amounts to nothing. Google is the leader in digital advertising and Google Cloud Platform is the third largest cloud vendor, and both markets are expected to grow quickly. According to Grand View Research, ad tech spend will increase at 13.7% annually to reach $2.4 trillion by 2030, and cloud computing spend will climb at 14.1% annually to reach $1.6 trillion during the same period.

With that in mind, investors can reasonably expect Alphabet to grow revenue at 14% annually through the end of the decade. That makes its current valuation of 5.6 times sales look reasonable. Investors should buy a few shares of this FAANG stock at that price.