When I started my career as a financial advisor some 30-plus years ago, I was taught the business from a fundamental perspective. In other words, companies with a strong balance sheet, growing top and bottom lines, and multiple sources of growth were worth a look.

But companies that spend indiscriminately yet are still darlings of Wall Street purely because of revenue growth, or those whose management style I disagree with? No thanks. All these years later, not much has changed.

Close-up picture of bear and bull statues on a downtown sidewalk.

Image source: Getty Images.

Profits, anyone?

The bullish sentiment cybersecurity provider Palo Alto Networks (NYSE:PANW) has enjoyed for years has been somewhat muted but is still overly optimistic in my opinion. Things got so out of whack early this past summer that at one point an analyst had a mind-boggling price target of $215 a share.

The reason for so much optimism is Palo Alto continues to report significant revenue gains every quarter. Though no longer in the 50%-plus range as it was for nearly two years running, last  quarter's -- Palo Alto's fiscal fourth -- $509.1 million in sales was a 27% jump, and its $1.8 billion for the year was a 28% improvement.

So, what's not to love?

For the quarter, Palo Alto  spent $245.4 million on sales costs alone, equal to 48% of total revenue. Sure, Palo Alto's top line grew 27%, but operating expenses climbed 24% to $397.9 million -- which is why operating losses rose again, and its earnings per share (EPS) jumped to a negative $0.42 a share compared to a loss of $0.35 a share a year ago. As an investor who appreciates an efficiently run company that consistently grows its bottom line, Palo Alto doesn't even come close to a stock I'd buy.

Surprise, surprise

The next stock I'd never buy will likely surprise, and possibly irritate, some investors. The reason I'm bearish on Apple (NASDAQ:AAPL) and always have been -- yes, I recognize shareholders have enjoyed excellent returns over the years -- is twofold. One, I have the same concerns from a financial perspective as I always have: Apple continues to generate the majority of its revenue from one product.

Of Apple's $8.7 billion in net income last quarter, 55% came from iPhone sales. Apple's dogged refusal to develop a lower-cost phone for emerging markets, which is where much of the smartphone growth is expected to come in the years ahead given saturation concerns, leads to the second reason I'd never buy its stock. Ego.

Apple's "it's my way or the highway" treatment of its suppliers is just one example of a company that acts like a bully in the neighborhood rather than a conscientious corporate leader. And why, with nearly $77 billion in cash and equivalents on the balance sheet, and almost $200 billion overseas, does Apple pay shareholders a measly 1.6% dividend? Because it can, and if you don't like it: Tough. No thanks -- Apple's fanatical customer base can invest all it wants in its shares. I'd never touch it.

On a positive note

The polar opposite to Palo Alto and Apple is Microsoft (NASDAQ:MSFT), which is why I'd consider buying its stock. CEO Satya Nadella is delivering on his "cloud-first" mantra in a big way, growing both revenue and profits, and Microsoft is an ideal example of a responsible corporate leader that doesn't throw its weight around to the detriment of its "partners."

From a financial perspective, Microsoft's 13% jump in revenue last quarter to $23.3 billion was remarkable given it's still relatively early in its transition to the cloud, artificial intelligence (AI), and augmented reality (AR), among other cutting-edge markets.

With a more than $18.9 billion annual run rate, Microsoft is one of, if not the, leading cloud provider on the planet. With its varied Software-as-a-Service (SaaS) product suite, Microsoft will continue to lead the cloud wars, and its success shows where it counts: profitability. Last quarter's $0.83 EPS was more than double the year-ago period's $0.39, and there's no end to its growth in sight thanks to its multiple product offerings. Now, that's a stock I'd buy.

Teresa Kersten is an employee of LinkedIn and is a member of The Motley Fool's board of directors. LinkedIn is owned by Microsoft. Tim Brugger has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Apple. The Motley Fool recommends Palo Alto Networks. The Motley Fool has a disclosure policy.