It's long been the case that if you wanted growth you looked to Chevron (CVX 0.75%), and if you wanted stability then you looked to ExxonMobil (XOM -0.09%). While this is still the case, investors are becoming increasingly concerned that as Chevron is overstretching itself as it continues driving for growth. If this is true, it could now be a risky investment. 

Huge expensive projects
The market has long been optimistic about Chevron's long-term outlook. The company has a number of projects coming onstream during the next few quarters, which will drive production and earnings higher.

Until these projects come onstream, though, Chevron is going to struggle. The development of these projects and associated project delays, especially in the case of Chevron's huge Gorgon LNG project in Australia, have put pressure on the company's cash flow.

As of yet, it's not clear if Chevron will be able to recover from this pressure anytime soon.

On a trailing twelve month basis, Chevron's free cash flow came in at -$484 million, down from $2.9 billion reported during the previous 12-month period. This is significantly below the company's all-time high free cash flow of $14.6 billion reported during 2011.

Additionally, during the first quarter of this year, Chevron's debt to equity ratio hit a high of 13% as the company borrowed to fill holes in its free cash flow figures, a number not seen since 2005.

Meanwhile, Exxon's outlook is rosier. While Chevron is driving for production growth, Exxon is targeting stability while reducing costs and improving upstream probability.

Stability and profit
Exxon is planning to cut capital spending over the next few years. Spending went from $42.5 billion last year to $40 billion this year, and is expected to average $37 billion per annum through 2017. Chevron, meanwhile, is planning to spend $40 billion per annum through 2016.

ExxonMobil is planning to use this capital wisely. The company is looking to increase profitability in its upstream segment by focusing on higher-margin production. Management is also targeting a higher percentage of liquids production, aiming to drive production of liquids from 52% currently to 69% by 2017.

This focus on free cash flow should drive free cash flow growth and underline investor returns.

Catching up
Hopefully, Exxon's drive to boost margins and target growth from existing projects should help the company return to its position as the more profitable company.

Despite being the smaller of the two, Chevron is actually the more profitable company at the moment; it reported gross and operating margins of 41.1% and 15.7% respectively for 2013. In comparison, Exxon reported margins of 30% and 13.2% for the same period.

Still, Exxon managed to crank out the better return on invested capital for the period, reporting an ROIC figure of 17.4% compared to Chevron's 13.5%.

Foolish summary
This is a relatively quick analysis of Chevron and ExxonMobil. However, it does outline the key differences between the two companies.

Chevron and ExxonMobil are now two completely different investments. With Chevron's capital spending rising to a higher level than Exxon's despite Exxon being the larger company, it is reasonable to suggest that Chevron is both set for growth and a risky investment. Chevron's spending is actually rising faster than its income, so the company is having to borrow to fill the gap. This is bad news for defensive investors.

ExxonMobil just looks to be the all-round safer play.