Warren Buffett's disclosure of Berkshire Hathaway's (NYSE:BRK-A) (NYSE:BRK-B) holdings last Friday probably made a couple of meaningful points.

The first is obvious: Despite being the most revered investor of our times -- or perhaps all time -- Buffett, along with his team of helpers, is capable of heading down the wrong investment path. On the energy front, he demonstrated that by snapping up ConocoPhillips (NYSE:COP) shares for Berkshire at or near the top of their run.

In addition, an economy that continues to teeter wildly hasn't helped the Oracle of Omaha -- or anyone else, for that matter. Nevertheless, Buffett is proving that he can take his medicine like the rest of us. His team has been unloading Conoco shares hand over fist, taking a drubbing in the process.

But secondly, this massive investment in Conoco, which made Berkshire the Houston-based oil company's largest shareholder, proved that, despite the manner in which we tend to lump them together, all Big Oil companies are not created equal. As to the second point, take a quick look at the table below, which shows how Big Oil companies have fared relative to their 52-week highs.

Company

52-Week High

Price 5/15/09

Decline

BP (NYSE:BP)

$77.69

$45.62

41%

Chevron (NYSE:CVX)

$104.63

$65.88

37%

ConocoPhillips

$95.96

$43.93

54%

ExxonMobil (NYSE:XOM)

$96.12

$69.11

28%

Shell (NYSE:RDS-A)

$88.73

$48.43

45%

I frankly haven't a notion why Buffett and his team settled on ConocoPhillips for a buying spree last year, something he now calls a mistake. It clearly has been the laggard among the big integrated companies in year-to-date performance, and the company also was the caboose among the group regarding last quarter's earnings slide versus the prior year.

However, Conoco finishes behind only Exxon in share price recovery, as crude has ascended from its early-year lows. I'm not certain I'd be selling it today if I owned it at much higher levels, although Buffett maintains he's doing so for tax reasons.

I also believe that crude's upward movement since February virtually mandates that Fools -- after careful analysis -- include at least a minimal energy component among their investments. On that basis, I'll sign off with a pair of specific thoughts on this subject.

First, I'd avoid buying shares in ConocoPhillips, given its low reserve replacement ratio and relative standing in the group. I've said repeatedly that I think ExxonMobil remains the qualitative and quantitative star of the show. I haven't changed my mind.

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Fool contributor David Lee Smith doesn't have financial interests in any of the companies mentioned above. He does, however, welcome your questions or comments. Berkshire Hathaway is a Motley Fool Stock Advisor selection, a Motley Fool Inside Value recommendation, and The Fool owns shares of it. Try any of our Foolish newsletters today, free for 30 days. The Fool has a mistake free disclosure policy.