Investing in growth stocks can be exciting and rewarding, especially for shareholders willing to focus on businesses that can sustain that growth over the long term. But finding those stocks is easier said than done.

So we asked three top Motley Fool investors to each pick a growth stock for the long term that you should consider buying now. Read on to see why they chose Chipotle Mexican Grill (NYSE:CMG), Baidu (NASDAQ:BIDU), and iRobot (NASDAQ:IRBT).

A woman in a suit drawing a line indicating exponential growth


Sooner or later, Chipotle will rise again

Steve Symington (Chipotle Mexican Grill): With shares down more than 30% from their 52-week high set in May, it's been a tough few months to swallow for Chipotle investors. But I think long-term shareholders stand to win big as Chipotle claws its way back to the top of the fast-casual restaurant space.

To be fair, I've pounded the table to buy Chipotle more than once in recent months, even arguing in mid-July that shares were incredibly cheap considering both its earnings potential and its already beaten-down stock on the heels of a norovirus outbreak that temporarily closed one of its more than 2,300 locations in June. Shares have continued to drift lower since then, however, as a chorus of skeptics have doubted the positive potential for traffic- and sales-driving initiatives -- including its nationwide queso rollout and carefully implemented price increases -- to achieve their desired results.

Investors will receive their next update to that end when Chipotle announces third-quarter 2017 results after the market closes on Tuesday. If the skeptics are proven wrong, rest assured that Chipotle stock will skyrocket in response. If the naysayers are right, however, I expect shares to pull back even further and create an even more attractive buying opportunity for long-term investors to open or add to their positions. Either way, I'm convinced that this solidly profitable, steadily growing restaurant concept will return to its winning ways.

The biggest search engine in China

Leo Sun (Baidu): Baidu controls about 80% of the internet search market in China, which puts it in a prime position to profit from rising internet penetration rates across the country. China currently has an internet penetration rate of just 52%, compared to 89% in the U.S. and 91% in Japan.

Like its western counterpart Google, Baidu expanded its ecosystem to include other portal sites, mapping services, streaming video, an artificial intelligence-powered virtual assistant, and even autonomous cars. It also invested heavily in the growth of its online-to-offline (O2O ecosystem), which allows users to hail rides, order food deliveries, make mobile payments, and access other services without leaving its mobile app.

Baidu's revenue growth slowed down significantly in fiscal 2016, due to two one-time events: a government crackdown on misleading ads (mostly for healthcare products) and a swap of its stake in online travel agency Qunar for an equivalent stake in Ctrip (NASDAQ: CTRP). But with both issues now settled, analysts expect Baidu's revenue and earnings to rise 22% and 25%, respectively, this year.

Baidu trades at 33 times next year's earnings, which isn't cheap but easily justified by its long-term growth potential. It still faces ongoing challenges from its ecosystem rivals Alibaba (NYSE: BABA) and Tencent (NASDAQOTH: TCEHY), but its dominance of the search market makes it one of the best long-term plays on China's growth.

What the shorts are missing on this long-term growth story 

Jason Hall (iRobot Corporation): Over the past couple of months, the market has swept the floor with robot vacuum leader iRobot, beating shares down 27% following a short-seller targeting the company. In short (please forgive the pun), Spruce Point Capital thinks that SharkNinja's (you can't make this stuff up) entry into the robot vacuum market is a major threat to iRobot.

In fairness, SharkNinja has had huge success in both the high-end blender and people-powered vacuum segments, with a track record of taking market share. And it very well could take some share away from iRobot in the coming years. But I'm not worried -- to the contrary, I'm far more likely to buy shares than sell on either a new competitive entrant or Spruce Point's somewhat flawed short thesis. 

To start, this is a major growth industry. Robot vacuums are a small share of the total market. Also, iRobot's innovation lead and strong portfolio of patented technology could prove to be much harder to overcome than what SharkNinja has faced before. The road iRobot has already traveled is littered with failed attempts by many serious competitors to crack the market. That's before we factor in the potential for nonvacuum products, such as the Braava mop, to deliver big growth. 

My money's on the founder-led iRobot, with the best products, a deep technology lead that it's building on, and decades of growth potential. Spruce Capital may have given long-term investors a buying opportunity. 

Jason Hall owns shares of Chipotle Mexican Grill and iRobot. Leo Sun owns shares of Baidu. Steve Symington owns shares of iRobot. The Motley Fool owns shares of and recommends Baidu, Chipotle Mexican Grill, and iRobot. The Motley Fool recommends International. The Motley Fool has a disclosure policy.