Does today's update make Petrofac plc a BETTER buy than Royal Dutch Shell plc or BP plc?

With the impending EU referendum diverting investors' attention for at least two more days, a cynic would say that now is arguably as good a time as any for a company to release bad news to the market.

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With this in mind, let's look at the key figures from this morning's trading update from oil services company, Petrofac(LSE: PFC).

Bulging order book

Operating in 29 countries, Petrofac designs, builds operates and maintains oil and gas facilities. Investors brave enough to have invested in the company in late 2008 will have seen their shares rise over 600% to 1,743p by April 2012. Of course, it won't come as a surprise to learn that these shares have languished more recently as a result of the oil price slump (and several problematic projects). They now exchange hands for just 749p.

Today's trading statement contains few surprises. Net profit is expected to be in line with previous guidance and evenly split between the first and second half. The order book now stands at $18.9bn, giving "excellent revenue visibility for this year and beyond," according to the company. While this is positive, net debt is expected to increase to around $1.1bn by the end of June due to capex and payment of last year's final dividend. The company announces its next set of interim results on 30 August.

Buy the giant?

A price-to-earnings (P/E) ratio of just 9 suggests Petrofac's shares are cheap and a gradual rise in the price of crude will do the company no harm at all. That said, are investors better off loading-up on FTSE 100 oil giants Royal Dutch Shell(LSE: RDSB) or BP(LSE: BP)?

Having merged with BG Group earlier in the year, the former has cut back on capex with the aim of preserving its dividend. Shell now trades on a P/E of 22 for 2016, reducing to just 13 next year and currently yields over 7%. BP currently trades on a P/E of 29, reducing to around 14 next year. Like Shell, BP offers a massive yield of over 7% and will need to dip into reserves in order to fund this payout. However, if you fancy the latter's dividend, you'll need to act fast as the ex-dividend date is 30 June.

Worth the risk?

The problem with investing in any commodity-focused company is that future earnings will always be controlled to some degree by external factors. And while companies can work at reducing costs, this will only go so far for so long. Understandably, this puts pressure on their abilities to pay dividends.

While Petrofac's payout appears the most secure (covered 1.8 times in 2016), a reduction in the order book over the next few years could see a cut. Moreover, I'm concerned that the dividend has hardly changed since 2012. A decent-sized-but-growing yield is what income investors should be looking for. The stagnant payout, combined with the huge amount of debt that the company now carries make me wary of the shares.

While busy fighting its own battles, I think Royal Dutch Shell's shares offer more upside (and more so than BP's) as dividends look more secure following a period of belt-tightening. The recent merger, combined with the CEO's commitment "to reshape and simplify the company," gives me confidence that that it will overcome the challenges currently faced by the industry.

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If you had put £100 into the UK stock market in 1945, the shares would have had a nominal value of £9,148 after inflation 70 years later (Barclays Equity Gilt Study, 2015). However, if you had also reinvested all dividends received over this period, this figure would jump to a quite amazing £179,695.

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Paul Summers owns shares in Royal Dutch Shell B. The Motley Fool UK owns shares of and has recommended Petrofac. The Motley Fool UK has recommended BP and Royal Dutch Shell B. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.