No one can claim that Cathie Wood isn't bullish about artificial intelligence (AI). She has been a vocal cheerleader for AI for years, and her Ark Invest funds have invested heavily in AI stocks.

However, there's one high-flying AI stock that Wood isn't so bullish about these days. She recently spoke at an investor conference in Munich, Germany, where she made two big knocks against Nvidia (NVDA 6.18%). Wood also talked up two AI stocks that she likes more right now. 

Two big knocks against Nvidia

Wood's first knock against Nvidia at the Munich conference isn't surprising. She noted that the stock is "easy, but it's also really expensive." That isn't the first time she's commented about the chipmaker's steep valuation. On May 29, Wood tweeted that Nvidia was "priced ahead of the curve." At the time, the stock was up 167% year to date. It's even higher now.

Her second big knock against Nvidia was that it's "very obvious." What did Wood mean by that comment? Pretty much every investor knows that Nvidia is benefiting from the generative AI boom. She said that Ark Invest is "really focused on those companies that most people aren't talking about right now."

Again, this isn't a surprise. Ark Invest issued a report last month that focused on the valuations of AI stocks. The report acknowledged that Nvidia "is likely to remain a prime enabler and beneficiary of continued breakthroughs in AI." However, it added that "many other potential beneficiaries are not well understood, may sell at much lower valuations, and potentially could deliver significant revenue and earnings surprises on the high side of expectations." 

Two better AI picks, according to Wood

So what are some of those AI stocks that few investors are talking about right now that Wood likes more than Nvidia? She singled out two at the Munich conference: Twilio (TWLO 1.47%) and UiPath (PATH 0.26%).

Twilio markets a customer engagement platform that gives developers customizable APIs (application programming interfaces) to integrate real-time communications within their software applications.

Customer communications is a natural application for generative AI. Ark Invest believes that Twilio is ideally positioned to lead the way. Twilio is certainly focused on AI. CEO Jeff Lawson said in the company's second-quarter conference call that Twilio is using large language models to "help customers enter the AI race multiple steps ahead of their peers."

UiPath is a leader in robotic process automation (RPA). The company's objective for its RPA platform is to perform any task a person does digitally faster and more consistently. 

Ark Invest thinks that UiPath has a key advantage over rivals in the RPA market with its low-code, no-code interfaces. It's not the only big-name fan of UiPath. Alphabet has invested in the company, holding over 14 million shares as of June 30. Google Cloud is also partnered with UiPath.

Wood said she believes in these lesser-known AI stocks enough to put a lot of money into them. Twilio now ranks as the eighth-largest position across all of Ark Invest's portfolio. UiPath is the second-biggest holding.

Why Wood could be right

There's no question that Wood is right about Nvidia being an "obvious" AI pick. She's also correct that the stock sports a high valuation. Even after its recent pullback, Nvidia still trades at nearly 40 times expected earnings.

But is Wood also right about Twilio and UiPath? Maybe. Both companies could have tremendous long-term growth prospects. It's not hard to envision AI providing huge tailwinds for Twilio's customer engagement platform and UiPath's RPA platform.

However, neither Twilio nor UiPath is all that cheap right now, based on their forward earnings multiples. Wood clearly thinks the two companies will be able to deliver enough growth to justify those valuations. She correctly predicted that Nvidia would be a big winner years ago. She just might be on target about these two AI stocks as well.