It's been a great eight months for investors since ConocoPhillips (NYSE:COP) spun off Phillips 66 (NYSE:PSX). Both have trounced the return of the S&P 500 as investors have realized the true value of the assets. As you can see from the following chart those investors that held on to their Phillips 66 stock have done especially well:

COP Total Return Price Chart

COP Total Return Price data by YCharts

However, now that the value has been unlocked, which company is a better buy?

Still time to fill up on PSX?
For Phillips 66 investors the timing of the spinoff couldn't have been better. It just so happens that we're going through a bit of an energy boom here in the U.S. That boom is sending down the prices of the feedstock Phillips 66 needs to run though its refineries and petrochemical facilities. That's giving once disadvantaged businesses a major competitive advantage.

Pipeline capacity is so tight that oil coming out of Canada and the Bakken trades at a huge discount to Brent-priced crude. It's one reason why Phillips 66 just signed a five-year deal to ship Bakken crude to one of its refineries in New Jersey, despite adding $10-$15 per barrel in transportation costs. As the company continues to shift toward more advantaged crude, margins and cash flow will go higher.

Taking advantage of cheap crude oil for its refineries is just one way Phillips 66 is benefiting from the U.S. energy boom. The company's petrochemical joint venture will Chevron (NYSE:CVX) will see the same advantages from the growth of natural gas liquid production. The 50/50 joint venture, CP Chem, is investing in several petrochemical projects along the Gulf Coast to further grow its usage of cheap feedstocks. Again, as these projects come on line so will increased earnings for Phillips 66.

Advantage lost?
What's an advantage to Phillips 66 might be seen as a disadvantage to its former parent. As one of the largest producers in North America, ConocoPhillips has large land positions in almost all of the top production basins. Some of those large land positions in Canada, the Bakken, as well as a large natural gas business, are causing ConocoPhillips margins to be a bit squeezed.

That's especially true for its natural gas business as a $0.25 per million cubic feet change in the price of gas at Henry Hub can affect its income by up to $125 million. Meanwhile, a dollar per barrel change in either West Texas Intermediate or Western Canadian Select can yield about a $25 million change in the company's income. Right now the company is being negatively affected by both; however, over time as more pipeline capacity and demand comes online it'll have a positive effect on the company's bottom line. 

What investors might miss is the company's international production. With conventional projects in Europe, deepwater activities in Malaysia and liquefied natural gas in Australia, ConocoPhillips is poised to shift more production to these higher-margin projects. Taken together and ConocoPhillips offers investors growth, income and deep value.

My Foolish take
As an investor in both I don't plan on selling my shares in either company. However, I think that there is much more upside in ConocoPhillips over the longer term. It's just too cheap at less than eight times earnings and with a dividend of more than 4% you'll be paid well as the company continues to execute on its plan to focus on high return projects.

Fool contributor Matt DiLallo owns shares of Phillips 66 and ConocoPhillips. The Motley Fool recommends Chevron. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.