The question of which company holds the more valuable brand, Coca-Cola (NYSE:KO) or PepsiCo (NYSE:PEP), is as ageless as the famous Pepsi Challenge. With the battle lines drawn, carbonated beverage connoisseurs take their soda of choice very seriously. But does this passion translate to domineering profits for the kings of cola?

Millward Brown's annual BrandZ ranking bestows top honors to the best global brands. The rankings are determined through research with 150,000 consumers from more than 30 countries, along with financial data and earnings prospects. The recently released 2014 edition showcases Coca-Cola and PepsiCo (NYSE:PEP) products as BrandZ' most valuable soft drinks.

Impressively, both Coca-Cola and Pepsi have secured spots on the BrandZ list since its 2006 inception. Although Coca-Cola slipped one spot from No. 5 in 2013 to No. 6 on the overall list this year, Pepsi plummeted 13 spots on the list. It currently sits at No. 88, down from No. 75 on last year's list. Coke's nearly $80.7 billion brand value increased 3% over the past year. However, Pepsi's almost $11.5 billion brand value fell 5% during that same period. 

Of the top 15 soft drinks on the BrandZ list, five are Coca-Cola offerings and six are PepsiCo products. The collective brand value for all five of the Coke products is nearly $93 billion. Meanwhile, the aggregate brand value for the six Pepsi offerings is $25 billion. Dr Pepper Snapple Group, Nestle, and Red Bull own the other four brands on the list, which are Dr Pepper, Nescafe, Nespresso, and Red Bull.

Dissolving demand
Americans don't guzzle soft drinks like they used to. That's a bitter fact for soda companies to swallow. In their struggle to reverse the decline in U.S. soda consumption, soft-drink makers have commanded increased soda prices to combat loss of volume sales. But they've recently faced a more worrisome problem: declining revenue. In order to combat sluggish sales, both Coca-Cola and PepsiCo have grown the breadth and depth of their portfolios with particular focus on noncarbonated drinks, which are expected to outpace carbonated.

In the past year, PepsiCo's carbonated brands lost value while its noncarbonated ones gained value. For example, carbonated Mountain Dew, Pepsi, and Diet Pepsi brands lost 7%, 5%, and 3%, respectively, of brand value during the past year. Meanwhile, noncarbonated Gatorade and Tropicana enjoyed gains, with brand values soaring 10% and 8%, respectively, during that same period. Not surprisingly, Coke's carbonated Diet Coke brand lost 5% of brand value last year, while its Minute Maid juice brand value increased 8%. Yet remarkably, Coca-Cola's carbonated Fanta and Sprite brand values grew 23% and 10%, respectively.  

Do the best soda brands refresh shareholders?
The companies behind these brands have returned stellar profits to their stockholders over the course of their publicly traded lives. However, PepsiCo -- returning roughly 5% -- has edged out the S&P 500's 4% year-to-date return. By comparison, Coca-Cola has actually lost almost 1% during that same period. PepsiCo's recent success has been attributed to strength in its salty snacks business

Yet, when we look at performance over a longer period of time, a different picture bubbles to the surface. Coca-Cola edged out both PepsiCo and the S&P 500, by returning nearly 115% over the past decade. Meanwhile, the S&P 500 returned only 111% during that same period. By comparison, PepsiCo returned 109%. 

But focusing solely on past performance is like driving a car using only the rearview mirror. It gives us no indication as to how these companies might achieve success in the future. Instead, investors must focus on factors like forward-looking industry trends, growth prospects, and profitability. Both cola giants face uphill battles with regards to declining soft drink consumption and legislative risks like soda taxes . However, PepsiCo's snack offerings, which include Quaker oatmeal, Stacy's pita chips, Sabra hummus, and many other products, which comprise 52% of company sales,  help spread these risks and lend it one key advantage over its major rival.

Foolish final thoughts
Collectively, Coca-Cola and PepsiCo boast nearly 250 years of experience. The endurance of these companies, coupled with their respective brand strengths, has helped them build worldwide exposure. Coke, however, was crowned 2014's most valuable soft-drink brand.