In the integrated energy space, two companies reign supreme. Not surprisingly, they are ExxonMobil (NYSE:XOM) and Chevron (NYSE:CVX). These are both giants in the oil and gas space. ExxonMobil and Chevron hold huge market capitalizations of $439 billion and $250 billion, respectively. They are also both integrated majors, meaning they have operations on every side of the business. ExxonMobil and Chevron are involved across oil, natural gas, and chemicals and operate both upstream and downstream businesses.

But it would be a mistake to think they're identical. Despite their many similarities surrounding project lineups and operational focus, there are indeed some differences that you should know about. The major differences between ExxonMobil and Chevron pertain to their capital returns. The two companies hold different philosophies about how best to return cash to shareholders between share repurchases and dividends.

If you're considering an investment between ExxonMobil and Chevron, here's what you should know.

Impressive project lineups
Both ExxonMobil and Chevron have several high-profile projects set to ramp up over the next couple of years. One specific area is in liquefied natural gas, or LNG. Both companies see this as a major opportunity, and that is especially true when it comes to emerging markets in Asia, where demand is robust.

ExxonMobil's emerging market LNG initiative is located in Papua New Guinea. This is a $19 billion project with an expected life span of 30 years. The company expects production to total 9 trillion cubic feet of gas, with an annual production capacity of about 6.9 million tonnes. First shipment just occurred ahead of schedule, meaning the benefits should be felt shortly. The project involves several production and processing facilities stretched across several provinces of Papua New Guinea, and it is all connected by roughly 435 miles of pipelines.

For Chevron's part, it holds two separate LNG facilities located in Australia, and it has the same ambitions in mind, which are to serve the rapidly growing Asian economies. Chevron's projects are named Wheatstone and Gorgon and are nearing the final stages of completion. Gorgon is about 80% complete, and management expects first shipments next year. The facility includes a 15.6 million tonne per annum LNG plant. 

Meanwhile, Wheatstone is a $29 billion project with annual production pegged at 8.9 million tonnes per year, which will take a little longer to finalize. First shipment is expected in 2016.

Not forgetting about oil
In addition to LNG, both ExxonMobil and Chevron hold huge oil projects. ExxonMobil's Kearl undertaking, located in the Canadian oil sands, began first production a year ago. The initial phase calls for production of 110,000 barrels per day. By late 2015, the company believes production capacity will double from initial levels. Over the long term, the possibility presented by the Kearl project is huge. Production is expected to total 4.6 billion barrels over a 40-year time frame.

Meanwhile, Chevron's oil pursuits are heavily concentrated in the Gulf of Mexico. Two particularly promising sites are the Jack/St. Malo and Big Foot developments, which are slated for start-up this year and next year, respectively. Cumulatively, the projects hold the potential to add 256,000 barrels of oil to Chevron's average production. This in itself represents 35% growth from Chevron's North American production last year.

Shareholder rewards differ
While ExxonMobil and Chevron are targeting similar project ramp ups going forward, they differ on rewarding shareholders. ExxonMobil has long maintained a preference toward share buybacks, while Chevron offers a higher dividend yield.

ExxonMobil has bought back $84.2 billion of its own shares over the past five years. It bought back $13 billion of its shares just last year. By contrast, Chevron repurchased just $5 billion in stock last year.

Chevron doesn't leave investors wanting, however. It offers a 3.2% payout, about 50 basis points higher than ExxonMobil's 2.7% yield.

The bottom line is that both companies are prodigious cash-generators that reward their investors handsomely. If you're a die-hard income investor, you may prefer Chevron based on its higher dividend, but both companies have great project lineups and return billions to shareholders every year.