Source: AutoZone

The past two days have been pretty odd for AutoZone (AZO -1.80%). In spite of the company beating analyst estimates on both the top and bottom lines, shares of the auto parts supplier fell 4% on May 27 before popping up 2% the next day on news of an analyst upgrade. Given all this confusion over the value the company brings and its prospects moving forward, is now a prime time to jump in and buy a stake or would O'Reilly Automotive (ORLY -2.78%) or Advance Auto Parts (AAP -2.69%) be better plays for the Foolish investor?

AutoZone's results impressed nobody except for Gabelli
For the quarter, AutoZone reported revenue of $2.34 billion, narrowly outperforming analyst estimates of $2.33 billion and coming in a whopping 6% higher than the $2.21 billion management reported the same quarter a year earlier.

According to the company's earnings release, the main driver behind its increase in revenue was a 4% rise in comparable store sales. However, the business also benefited from a 3% jump in the number of stores outstanding to 5,279 this year versus the 5,109 the company operated at the end of the third quarter last year.

Source: AutoZone

From an earnings perspective, AutoZone performed nicely as well. For the quarter, management reported earnings per share of $8.46, $0.02 more than forecasted and 16% greater than the $7.27 the business enjoyed last year. While increased sales played a role in the company's higher earnings, the biggest contributor was the 8% drop in share count year-over-year.

In light of these operational improvements, analysts at Gabelli upgraded the company from "hold" to "buy". This decision by the firm came in spite of concerns by investors that AutoZone's rising inventory (which increased 12% compared to last year's quarter) may result in lower returns for the business down the road.

Is there a better road to drive down?
The past few years have been very kind to AutoZone and its shareholders. Between 2009 and 2013 alone, the business saw revenue climb 34% from $6.8 billion to $9.1 billion as higher aggregate comparable store sales of 22% and an 18% increase in store count had a positive impact on the company's performance.

Source: AutoZone

Over this same five-year period, rival Advance Auto Parts has seen its revenue increase 20% from $5.4 billion to $6.5 billion while O'Reilly Automotive's top line soared 37% from $4.8 billion to $6.6 billion. Like AutoZone, Advance Auto Parts also increased its store count by 18% during this period, but the company's comparable store sales growth of 14% left it behind the competition. Meanwhile, O'Reilly Automotive left both of its peers in the dust, with aggregate comparable store sales increasing 29% as store count rose 22%.

From a profitability perspective, the ranking between these companies remained unchanged. Over the past five years, AutoZone managed to increase its net income by 55% from $657 million to $1 billion as higher revenue was complimented by falling costs. During this period, management reported that its cost of goods sold fell from 49.9% of sales to 48.2% while its selling, general and administrative expenses dropped from 32.9% of sales to 32.4%.

AZO Revenue (Annual) Chart

AZO Revenue (Annual) data by YCharts

Advance Auto Parts continued to lag AutoZone, but its results were still strong. Over this timeframe, the company saw its net income jump 45% from $270.4 million to $391.8 million. Just as in the case of AutoZone, Advance Auto Parts saw its cost of goods sold and selling, general and administrative expenses fall in relation to sales but both of these metrics remained higher for the retailer than they did with its peer.

By far the best performer over this period has been O'Reilly Automotive, as evidenced by its net income growth, which skyrocketed 118% from $307.5 million to $670.3 million. This was due, in part, to the company's cost of goods sold and selling, general and administrative expenses improving (in relation to sales) far faster than its peers, but can also be chalked up to the company's interest expense staying virtually unchanged over the five-year period.

Foolish takeaway
Based on the data provided, it appears as though Mr. Market doesn't quite know what to do with AutoZone. Yes, the company did report a better-than-anticipated quarter, but the fact that inventories are rising rapidly could be cause for concern. From a big picture perspective though, investors shouldn't worry too much.

In spite of any short-term problems, the company's long-term performance has been strong and it's very possible that management can keep the company going down the right track. However, for the Foolish investor who's more interested in a faster-growing enterprise, O'Reilly Automotive might make for a better prospect. Even though there is no guarantee that the business can keep expanding rapidly, the fact that its long-term performance outstrips its peers should entice the Foolish investor to analyze the company in greater detail before discarding it.