Mid-cap stocks have the best odds of scaling into $100 billion corporations thanks to their tested business models and large addressable markets. But the many opportunities in front of them attract significant competition, spanning from industry behemoths with seemingly infinite resources to small, nimble players with chips on their shoulders.

Luckily for you, our mission at StockStory is to help you make money and avoid losses by sorting the winners from the losers. Keeping that in mind, here is one mid-cap stock with massive growth potential and two that could be down big.

Two Mid-Cap Stocks to Sell:

Twilio (TWLO)

Market Cap: $18.22 billion

Known for the clever "Twilio Magic" demo that had developers creating functioning communications apps in minutes, Twilio (NYSE: TWLO) provides a platform that enables businesses to communicate with their customers through voice, messaging, email, and other digital channels.

Why Is TWLO Not Exciting?

1. Customers had second thoughts about committing to its platform over the last year as its average billings growth of 13.5% underwhelmed
2. Estimated sales growth of 9.3% for the next 12 months is soft and implies weaker demand
3. Sky-high servicing costs result in an inferior gross margin of 49.4% that must be offset through increased usage

Twilio is trading at $122.15 per share, or 3.6x forward price-to-sales. Check out our free in-depth research report to learn more about why TWLO doesn’t pass our bar.

Omnicom Group (OMC)

Market Cap: $13.89 billion

With a vast network of creative agencies that helped craft some of the most memorable ad campaigns in history, Omnicom Group (NYSE: OMC) is a strategic holding company that provides advertising, marketing, and communications services to many of the world's largest companies.

Why Are We Wary of OMC?

1. Absence of organic revenue growth over the past two years suggests it may have to lean into acquisitions to drive its expansion
2. Capital intensity has ramped up over the last five years as its free cash flow margin decreased by 7.6 percentage points
3. Eroding returns on capital suggest its historical profit centers are aging

Omnicom Group’s stock price of $71.75 implies a valuation ratio of 8.2x forward P/E. To fully understand why you should be careful with OMC, check out our full research report (it’s free for active Edge members).

One Mid-Cap Stock to Watch:

Acuity Brands (AYI)

Market Cap: $10.6 billion

One of the pioneers of smart lights, Acuity (NYSE: AYI) designs and manufactures light fixtures and building management systems used in various industries.

Why Are We Fans of AYI?

1. Offerings are difficult to replicate at scale and lead to a stellar gross margin of 44.5%
2. Performance over the past five years was turbocharged by share buybacks, which enabled its earnings per share to grow faster than its revenue
3. ROIC punches in at 16.6%, illustrating management’s expertise in identifying profitable investments

At $348.19 per share, Acuity Brands trades at 17.3x forward P/E. Is now the time to initiate a position? See for yourself in our comprehensive research report, it’s free for active Edge members .

Stocks We Like Even More

If your portfolio success hinges on just 4 stocks, your wealth is built on fragile ground. You have a small window to secure high-quality assets before the market widens and these prices disappear.

Don’t wait for the next volatility shock. Check out our Top 9 Market-Beating Stocks. This is a curated list of our High Quality stocks that have generated a market-beating return of 244% over the last five years (as of June 30, 2025).

Stocks that made our list in 2020 include now familiar names such as Nvidia (+1,326% between June 2020 and June 2025) as well as under-the-radar businesses like the once-small-cap company Exlservice (+354% five-year return). Find your next big winner with StockStory today for free. Find your next big winner with StockStory today. Find your next big winner with StockStory today

StockStory is growing and hiring equity analyst and marketing roles. Are you a 0 to 1 builder passionate about the markets and AI? See the open roles here.