Big two likely to reward investors

A steady resurgence in commodity prices since November has not been fully reflected in the share prices of the big diversified miners like BHP Billiton and Rio Tinto.

Both companies have a strong suit in iron ore, a weak spot in aluminium and big growth plans for copper.

Both should benefit from continuing strong demand for coal and iron ore from Chinese customers, even if the steel scene is milder than this time last year.

Despite BHP's greater diversification, canny investors have a slight preference for Rio in the medium term based on a couple of factors.

First there is a belief that Rio's Pilbara ports are more easily expanded that BHP's, which would mean Rio could find it easier to increase its exposure to the iron ore cash cow in the decade ahead.

BHP meanwhile will have to spend a massive amount to build its outer harbour at Port Hedland - estimated to be more than $22 billion - and will have to commit an even bigger sum to develop Olympic Dam in South Australia.

Rio will not spend as much on growth, so it should enjoy more free cash flow in the next couple of years, and will have more capacity for share buyback programs and the like.

BHP's recent venture into shale gas, because of depressed gas prices in the United States, may be an investment that takes years to pay off.

Yet both the big miners remain a safer bet than Fortescue Metals Group, which is entirely leveraged to the iron ore price.

With Chinese buyers paying about US$140 for something that costs around $50 to produce, exposure to iron ore should continue to serve Fortescue well for many years to come. For this reason most analysts consider the company to be a good bet in the short-term at least.

Yet it is possible that last year's prices above $180 per tonne will never again be matched, as more and more supply comes into the market.

Fortescue will be among those increasing supply, but its growth targets are - as ever - are highly ambitious in terms of cost and schedule.

Two people associated with Fortescue's amazing six-year run founder Andrew Forrest and Manhattan-based investors Leucadia National have scaled back their involvement recently.

Mr Forrest has moved out of the chief executive's office and into a less hands-on role in the chairman's lounge. Leucadia meanwhile has been selling down a stake which once stood at 9 per cent. That stake is now below 1 per cent after another big sell down on January 25.

Just as television's Bewitched was never quite the same after the first Darren departed, investors can be forgiven for wondering if the best of the Fortescue party might now be behind them.