Today I’m looking at the investment case of two FTSE 100 giants.

Oil play in peril

Investor appetite for Shell (LSE: RDSB) has enjoyed a shot in the arm following unexpected strength in ‘black gold’ values over the past fortnight.

The Brent benchmark accelerated away from the lows of $27.67 per barrel struck in January (troughs not visited since 2003) and back above the $35 marker, thanks to fresh weakness in the US dollar.

Fossil fuel majors like Shell were unsurprisingly caught in the updraft, and the British business saw its own share price advance by almost a fifth in the fortnight from Brent’s lows.

Despite this strength however, broker projections indicate that Shell could prove a brilliantly-valued turnaround contender. City consensus suggests the oil giant will recover from a heavy bottom-line dip last year with a 7% advance in 2016, leaving the company dealing on a P/E rating of 12.2 times. On paper, any reading below 15 times is widely considered attractive value.

I’m not so convinced however, and see the bounce as nothing more than a fresh selling opportunity. Rather, I expect the sickly supply/demand imbalance to keep the oil sector firmly on the back foot.

Sure, Shell’s attempts to steady the ship by slashing costs and capex targets are essential in the current climate — the business announced 10,000 job cuts last week in the wake of 2015’s shocking results. But until crude demand steps solidly higher, and OPEC, Russia and the US finally bite the bullet and cut production, I reckon Shell’s earnings are set to keep falling in line with crude prices.

And while Shell defied calls for a dividend cut by keeping the 2015 payment frozen at 188 US cents per share, I believe investors should give expectations of a similar reward — yielding a chunky 7.7% — scant regard thanks to the firm’s weak profits potential and mounting debt pile.

Indeed, I reckon investors should be prepared for fresh earnings and dividend downgrades sooner rather than later.

Ring up delicious returns

Based on conventional metrics, it could be strongly argued that Vodafone (LSE: VOD) fails the acid test when it comes to being considered a hot ‘value stock.’ However, I would consider the telecoms giant a savvy selection despite its poorer ‘paper’ valuation relative to that of Shell.

The colossal costs of Vodafone’s Project Spring investment programme — combined with prior sales problems in its core European marketplace — are expected to push earnings 12% lower in the year to March 2016, the third successive fall if realised.

But unlike Shell, Vodafone has the fuel to generate powerful earnings growth in the years ahead, as the development of its data and voice services in established and emerging regions gives it the base to meet surging user demand.

Indeed, the City expects these measures to deliver a 19% earnings rise in fiscal 2017. And while a consequent P/E rating of 38.7 times may be considered heady at first glance, I believe Vodafone’s huge organic scheme should deliver smashing bottom-line growth further out and keep the multiple toppling.

And value hunters can take consolation in Vodafone’s excellent dividend prospects too. The London firm is anticipated to pay a dividend of 11.5p per share in both 2016 and 2017, resulting in a market-smashing yield of 5.3%.

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Royston Wild has no position in any shares mentioned. The Motley Fool UK has recommended 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.