This year has been a big one for artificial intelligence (AI) stocks, with these players leading gains in the S&P 500. Investors have piled into the stocks to get in early on a big market opportunity -- analysts forecast today's $200 billion AI market will reach beyond $1 trillion later this decade. That could equal significant revenue for companies using AI as well as those that develop AI products and services.

And today, some of these AI players already are scoring big wins in terms of earnings and stock performance. In fact, two top AI companies are trading at record highs right now after climbing in the triple digits since the start of the year. These players both have reported fantastic earnings and offer solid long-term outlooks -- but Wall Street says only one of them is a buy today. Let's zoom in on each of these AI leaders.

Nvidia (NASDAQ: NVDA) has become an AI empire over the past few years, selling not only its top graphics processing units (GPUs) but also a full range of products and services to support any AI project. This has resulted in triple-digit earnings growth quarter after quarter, and growth may be far from over. For three reasons.

First, as mentioned, the AI market is soaring and should continue to grow throughout the decade, offering ongoing revenue growth opportunities to companies in the space. Second, Nvidia already is a leader with the best-performing GPUs around, and that's led to demand for its products outpacing supply. Finally, Nvidia has pledged to update these GPUs annually, a key move that should keep it in the lead.

Nvidia shares may not be dirt cheap at 50 times forward earnings estimates, but considering the company's growth, gross margin of more than 70%, and long-term prospects, valuation looks reasonable. Though Wall Street's average price forecast calls for less than a 4% gain over the coming 12 months, analysts' average recommendation is a "buy." So, the general feeling is Nvidia is a stock to pick up today -- though it may not soar tremendously in the year to come, the stock still has what it takes to roar higher over the long term.

Palantir Technologies

Palantir Technologies (NYSE: PLTR) has been around for about 20 years and through most of its history, it's been associated with government contracts. But thanks to its leap into AI, Palantir's overall growth as well as its commercial business have taken off. For example, in the most recent quarter, Palantir reported its highest level of quarterly profit ever.

So, why are companies and governments flocking to this software company? Palantir, using AI, helps customers aggregate their data and make the best possible use of it. And this often produces game-changing results -- from increased efficiency to entirely new ways of getting business or projects done.

And Palantir has developed a genius way of introducing its Artificial Intelligence Platform (AIP) -- launched last year -- to potential customers. Palantir holds bootcamps to help businesses go from zero to a solid use case by the end of the camp. This has helped the company generate double-digit revenue growth in recent quarters and up its game in the commercial space -- commercial revenue growth now is surpassing the still strong growth in the government business. In the recent quarter, U.S. commercial revenue rose 55%, while government revenue increased 23%.

In spite of this strength, the average Wall Street recommendation is a "hold" and 12-month price forecasts call for a 32% drop in the stock. That's as the shares trade for 120 times forward earnings estimates. Though the long-term picture still looks bright, the idea is this hot stock has gotten pricey and may cool down in the months to come.

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Adria Cimino has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Nvidia and Palantir Technologies. The Motley Fool has a disclosure policy.

The views and opinions expressed herein are the views and opinions of the author and do not necessarily reflect those of Nasdaq, Inc.