Dividend aristocrats have been rewarding income investors with at least 25 years of uninterrupted, annual payout increases. Dependable dividend growth helps us separate the true dividend powerhouses from the wannabes. Among the 500 companies in the S&P 500 (SNPINDEX:^GSPC) index, only 54 have currently earned the title of Dividend Aristocrat.

But simply raising dividends every year isn't always enough. There are winners and losers even in this elite club.

So we asked a handful of Motley Fool Contributors to help us find that dividing line. They came up with one dividend aristocrat standing head and shoulders above the rest, and two to avoid despite their solid pedigrees. You'll find food distributor Sysco (NYSE:SYY), consumer goods veteran Procter & Gamble (NYSE:PG), and telecom giant AT&T (NYSE:T) on this list -- see if you can guess which stock belongs in what category.

Bob Ciura (Sysco): Food distributor Sysco is a Dividend Aristocrat to avoid. To be sure, Sysco does have a great track record of rewarding shareholders. The company has paid a quarterly dividend every year since it first went public in 1970, and has increased its dividend 46 times in that period. Clearly, Sysco has an impressive dividend history. But it's also true that Sysco's dividend growth rate has declined significantly over the past several years, which is indicative of the slowing growth of the food distribution industry.

In Sysco's most recent 10-K, it estimates there are more than 15,000 companies engaged in food distribution in the United States. Management states that the barriers to entry are very low as well. Since the cost of switching distributors is low, customers can make supplier changes very quickly. Making matters worse is that costs are rising across the industry. Competition and food inflation have significantly eroded Sysco's profits over the past several years. Sysco's profit in 2010 clocked in at nearly $1.2 billion, but has declined each year since. In fiscal 2014, Sysco generated $931 million in earnings.

Not surprisingly, this has had an effect on Sysco's dividend growth. Sysco has kept its reputation as a Dividend Aristocrat, but only because it's lifted its dividend by one penny per share each year for six years in a row. Its compound annual dividend growth rate over the past five years is just 3% per year, which barely kept up with inflation. The bottom line is that Sysco's 3% dividend yield is nice, but there are plenty of other Dividend Aristocrats that offer 3% yields, but with much higher dividend growth than Sysco.

Tamara Walsh (Procter & Gamble): Procter & Gamble gets top marks as a dividend aristocrat because of its reliable payout and strong cash flow. For starters, the company has paid a dividend for the past 124 consecutive years without fail. On top of this, P&G has increased that dividend for 58 straight years at a compounded rate of more than 9% a year. In fiscal 2014, the consumer products maker increased its dividend 7% to $2.45 per share, and returned $6.9 billion in dividend payments to shareholders during that period. This tells investors that Procter & Gamble knows how to put its shareholders first.

Income investors will also be happy to know that the stock's dividend yield of 2.82%, is markedly higher than the S&P 500 average yield of 1.90% today. Additionally, the company's payout ratio of 65%, means management should be able to continue paying a dividend well into the future. Moreover, Procter & Gamble boasts a portfolio of 23 brands that each generate between $1 billion-$10 billion in annual sales for the company. Ultimately, this will enable P&G to responsibly reward shareholders through dividend growth and share buybacks for many more years to come.

Anders Bylund (AT&T): Dividend investors should avoid AT&T at all costs, and here's why.

Yes, AT&T is a real cardholder to the dividend aristocrats' lounge. The company (and predecessor SBC Communications) has been raising its payouts without fail since 1985 -- which was the second year that AT&T paid dividends at all.

Moreover, AT&T offers the highest current dividend yield among all 54 of today's aristocrats. At 5.6%, ATT's yield is miles ahead of the silver medalist, hospital chain operator HCP (NYSE:HCP), and its 4.5% yield.

But there's something sneaky about AT&T's long-running dividend increases. You see, they barely qualify as raises at all.

I mean, compare and contrast AT&T's last 25 years of dividend increases to those of the other stocks mentioned in this roundup:

T Dividend Chart

T Dividend data by YCharts

On average, AT&T has boosted its dividend payouts by 4.3% a year over this two-and-a-half decade span. Procter & Gamble delivered annual raises of 10.2%, and Sysco's average increases raced ahead to 16.7%.

I'm actually being generous to AT&T in presenting averages over this very long period -- its payout boosts have actually been much slower in the more recent smartphone era. Meanwhile, AT&T's paralyzed share prices both provide an artificial boost to the dividend yield and undermine the true value of those payouts.

No, thanks. AT&T's payouts look generous today, but that won't last with such an indifferent attitude toward keeping the dividend policy healthy.