In the world of specialty mattresses, two companies stand out for their innovative products: Select Comfort (Nasdaq: SCSS), which makes the "Sleep Number" line, and Tempur-Pedic International (NYSE: TPX), manufacturer of "Memory Foam" mattresses.

In a totally unscientific experiment, I asked friends which bed set they thought was more popular: Tempur-Pedic or Sleep Number. The overwhelming response was Sleep Number -- and readers here who have not researched the companies would probably answer the same. The reason lies in the vast difference between the two companies' marketing.

While most people are aware of both companies' products, Select Comfort has an aggressive approach to advertising. Radio/TV ads present celebrity spokespeople -- spokes-sleepers? -- who rave about the product and tell the world their "sleep number" (mattress firmness setting). On a popular morning radio talk show, the hosts give personal endorsements of the mattress and discuss what their "sleep number" was the night before.

Tempur-Pedic, by comparison, does less marketing, mostly in print. In fact, the company only recently launched a larger advertising campaign tied to their newest "Cloud" product line. Tempur-Pedic relies more on word of mouth and in-store demonstrations.

So who sells more mattresses? The companies do not provide unit sales figures, but revenues provide some clues:

Company

FY 2010 Revenue

Select Comfort $606 million
Tempur-Pedic $1,105 million

Given that both companies' most popular bed sets are priced around $2,000, it appears that Tempur-Pedic is selling almost twice as many beds as Select Comfort.

Fans of either mattress might ignore their company's fundamentals, because its products are cooler than the other side of the pillow. But as long-term investors, we're concerned about stock price appreciation, not the size of the company or our personal belief that its products are great. We need to peek under the covers. A good metric to use when comparing manufacturers like Tempur-Pedic and Select Comfort is operating margin, which accounts for all expenses directly related to sales. Pay close attention to marketing's effect on the bottom line:

Company Cost of Goods Sold Marketing Expenses Other Expenses Total Expense Operating Margin
Select Comfort $227 $270 $57 $554 8.6%
Tempur-Pedic $550 $200 $110 $860 22.2%

All figures in millions. FY 2010 data.

Marketing expense is killing Select Comfort. Some 45% of the cost of every Sleep Number bed sold goes toward marketing, vs. 18% for Tempur-Pedic. Select Comfort's razor-thin margins mean lower cash flow and the risk of occasional negative earnings reports.

Tempur-Pedic trades at 27 times earnings versus Select Comfort's 23 times. Skeptics might also argue that Select Comfort is in better shape because it has no long-term debt. Plus, it has reasonable free cash flow (10.5% of revenue), although not as healthy as Tempur-Pedic's (15%). Mainstream mattress company Sealy (NYSE: ZZ), buried in debt, has just 2.5% FCF.

Remember, though, that if we're taking the long-term view, and stock price is our principal measure of success. If the past is any guide, Tempur-Pedic is a win, with 298% price appreciation over the past five years, compared to a 40% decline for Select Comfort and flat performance for Leggett and Platt (NYSE: LEG), manufacturers of bedding components used in conventional mattresses. Going forward, if you're thinking about investing in one of these stocks, Tempur-Pedic will likely give you a better night's sleep.

Fool contributor G. David Frye thinks sound investing advice is investors' best aid for a good night's sleep. He's owned a Tempur-Pedic "Classic" for many years. He also owns shares of TPX. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.