BHP Group Ltd (ASX: BHP) and Rio Tinto Ltd (ASX: RIO) are two of the biggest mining shares on the ASX.
Both are high-quality businesses. Both have world-class assets. Both can generate huge cash flows when commodity markets are favourable.
I would be happy to own either in a long-term portfolio.
But if I had to choose just one today, I would pick BHP shares.
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The case for Rio Tinto shares
Rio Tinto remains one of the strongest resources companies in the world.
Its Pilbara iron ore operations are among the best mining assets on the planet. They are large, low cost, and capable of producing enormous cash flow when iron ore prices are supportive.
That makes Rio Tinto a serious dividend stock when the cycle is working in its favour.
I also like the fact that Rio Tinto has been trying to broaden its future growth profile. The company has exposure to aluminium, copper, and lithium, as well as iron ore. That gives it more than one way to benefit from long-term demand for materials used in infrastructure, electrification, and energy transition.
For income investors, Rio Tinto can be very appealing. When profits are strong, the dividends can be significant.
The issue is that I think Rio still feels more exposed to the iron ore cycle than BHP. Iron ore can be an outstanding commodity when demand is strong, but it can also be unforgiving when prices fall or China's property and infrastructure activity disappoint.
That does not make Rio a bad buy. I just think BHP has a slightly stronger mix for the next decade.
Why I prefer BHP shares
BHP also has a world-class iron ore business. That gives it the same kind of cash flow engine that investors want from a major miner.
But I think BHP's copper exposure gives it the edge.
Copper is one of the commodities I am most positive on over the next decade. It is needed for electricity networks, renewable energy, electric vehicles, data centres, industrial activity, and broader electrification.
I also think copper supply will struggle to keep up with demand.
New mines can take years to approve and build. Existing mines face declining grades, rising costs, and political risk in some regions. That creates a very attractive setup for large producers with existing copper assets.
This is where BHP looks especially strong to me.
If copper prices remain elevated over the long term, BHP could be one of the best-placed miners on the ASX to benefit. Its scale, balance sheet, and asset base give it options that many smaller miners simply do not have.
The potash option
BHP also has another long-term growth lever in potash.
Its Jansen project gives the company exposure to fertiliser demand and global food production. This will not transform earnings overnight, but I like the strategic direction.
Potash is different from iron ore and copper, which adds another layer to BHP's commodity mix. Over time, it could make the business more diversified and less reliant on one or two major earnings drivers.
That is important when thinking in five-year or 10-year terms.
Foolish takeaway
I think both BHP and Rio Tinto are ASX mining shares worth buying.
Rio Tinto offers a powerful iron ore franchise, attractive dividends, and useful exposure to commodities beyond iron ore.
But BHP wins for me.
Its iron ore business remains excellent, its copper exposure looks very valuable, and its potash expansion adds another long-term growth option.
