At first blush, the two companies are similar enough that it seemingly doesn't matter which stock you own. Both make must-have cleaning supplies and other household consumables. A closer comparison of The Clorox Company (CLX -0.93%) and The Procter & Gamble Company (PG -0.19%), however, makes it clear that one is distinctly a better bet than the other.

P&G is the superior stock pick, but perhaps not quite for the reason you may think. Let's dig in.

Comparing Procter & Gamble to Clorox

You know the companies. Clorox is, of course, the outfit behind cleaning products of the same name although it also owns Glad trash bags, Liquid-Plumr, and Kingsford charcoal, just to name a few of its other brands. Tide laundry detergent is arguably Procter & Gamble's flagship product although it's also parent to Bounty paper towels, Luvs diapers, Gillette razors, and more.

Size-wise, P&G's market capitalization is nearly 20 times greater than Clorox's,which gives it a distinct advantage: a much bigger marketing budget. Last fiscal year, P&G spent nearly $8 billion on advertising alone. During that same period, Clorox spent $709 million. Both are about one-tenth of each respective company's typical annual sales.

The two absolute figures, however, are clearly miles apart -- and that makes a world of difference.

This is where P&G's sheer size matters

Don't misread the message. There are advantages to being small. Smaller companies are generally nimbler, for instance, while larger companies tend to be bloated with employees who simply manage that organization's unwieldy size.

On balance, though, corporate size helps more than it hurts. That's particularly true when the business is one as simple and commoditized as cleaning supplies and other consumer staples. Think about it. Consumers certainly have their preferred brands of detergent and household cleaners. But most consumers aren't exactly hyper-loyal to a particular brand anymore. Value is increasingly important.

As a recent survey performed by brand consulting firm Merkle notes, "Even of those [consumers] who define themselves as brand loyal, 76% say they would still buy from competitors if it were cheaper of [or] more convenient to do so." A similar survey taken by JungleScout suggests that coupons or discounts are now a key consideration for more than half of U.S. consumers' online purchases.

That's where Procter & Gamble can really flex its fiscal muscle. It has enough funding to consistently advertise and offer coupons in all the most important venues. Clorox doesn't. Indeed, depending on the year, P&G is often the world's single-biggest advertiser, dwarfing Clorox's promotional efforts and therefore not even giving it a chance to further penetrate more important (read "bigger") markets.

In other words, the size of your pocketbook matters. Underscoring this idea is the problematic price hike Clorox put in place for Kingsford during the first calendar quarter of this year, which was not mirrored by competitors. Although it's still the leading brand of charcoal, these price increases led the brand straight into a sales headwind that cost it at least some market share.

As Clorox CFO Kevin Jacobsen conceded in an interview with Reuters, "We have to invest some more money here." The question is, is there actually any money available to make such a marketing investment?

You want stocks with unfair advantages

Don't panic if you already own a stake in The Clorox Company. It's not competing head-to-head with Procter on every single front. It's still the market leader in handful of categories, in fact, like charcoal, trash bags, and disinfectant wipes. It's selling plenty of this stuff, and more.

The overarching message remains the same, though. That is, Procter & Gamble can afford to out-promote any and all competition in any of its product categories. Clorox's smaller marketing budget, conversely, leaves all of its consumer-packaged goods vulnerable to their respective competitors, which are often backed by bigger and better-funded companies.

These companies can include grocers' own private-label goods. These very same grocers, in fact, actually like the fact that Procter's marketing pockets are so deep. It can afford to heavily promote its own products, drawing a big shopping crowd into stores. Grocers don't rely on Clorox's products to serve the same purpose nearly as much.

Bottom line? It's not a fair fight. Procter & Gamble's got a huge advantage on a bunch of companies, including Clorox.