IT’S A TASK that vexes every self-respecting billionaire from China's mainland: finding a suitable mansion in Hong Kong. The former British colony is a small place, and the stock of billionaire-worthy residences hasn't kept pace with the exploding ranks of mega-rich mainland buyers. The two Mas, Alibaba executive chairman Jack Ma and Tencent CEO Pony Ma, have risen to the challenge in different ways.

Jack's approach to the problem has been straightforward. In 2007, three weeks after Alibaba's $25 billion IPO, he shelled out $38 million for the five-bedroom, 7,000-square foot penthouse of a luxury development in Hong Kong's Mid-Levels district. The purchase worked out about $5,400 per square foot, a record for Asia at the time.

But that appears to have been Jack's Hong Kong starter home. In 2015 Hong Kong's South China Morning Post identified Jack as the buyer of 22 Barker Road, a prime property atop Victoria Peak, the iconic neighborhood that has been home to Hong Kong's elite since the colonial era. The Post said Jack had purchased a 9,900-square foot, four-story house for a jaw-dropping $193 million, or about $19,500 per square foot, which at the time made the structure Hong Kong's most expensive residence per square foot.

Although 22 Barker Road is widely assumed in Hong Kong to the house that Jack bought, Jack himself has declined comment on the Post's report that he was the buyer. (A few months later Alibaba Group bought the Post for $266 million.). The house was a 70-year-old concrete fortress that once served as residence of the Belgian consul general: It sold nearly nine times what the previous owner, former chief executive of the Hong Kong stock exchange Francis Yuen, paid for it in 2000.

The property comes with a 20,000-square foot private garden and killer view of Victoria Harbor. As of mid-June, that's about all it came with: Workers had razed the house to the foundations, presumably as a prelude to a rebuilding project.

Pony paid $57 million in 2014 for a house in Repulse Bay on the island's south side. But his trophy purchase is in Shek O, Hong Kong's rugged southeastern peninsula, in a neighborhood that is even more exclusive than the Peak. Though only a 40-minute drive from the skyscrapers of Central, Shek O feels worlds away. Most of the peninsula is a protected country park covered in dense jungle. The district is famed for its beaches, craggy rock cliffs, and the spectacular ocean vistas from its undulating "Dragon's Back" hiking trail.

That trail affords the best view of Pony's property, 13 Big Wave Bay Road, one of about 20 grand mansions that surround a golf course at the peninsula's southern tip. The golf course is part of the Shek O Country Club, founded by the great British trading houses and still considered Hong Kong's most exclusive private club. The mansions belong to some of Hong Kong's most powerful business leaders.

According to 2004 article in the South China Morning Post "wealth is not the sole requirement" for occupying a Shek O mansion. New residents must win the blessing of the board of Shek O Development, the secretive private company that owns the country club and, since the 1930s, has leased the land on which the luxury properties are built. Houses on land controlled by Shek O Development are required to be of "European type," and cannot be sold, renovated or even painted a different color without the entity's permission.

Pony purchased the Shek O property from a Hong Kong shipping tycoon in 2009. He paid $61 million, and won approval to redevelop and more than double the size of the 8,000-square foot house. Analysts estimate that when the renovation is complete, his property will have quadrupled in value.

The only drawback: The development company's rules could make it hard to sell. Pony's property may be bigger and worth more on paper than Jack's, notes Bruce Li, associate director at real-estate and relocation company Asia Pacific Properties, but "if a seller can't get approval from the Shek O shareholders, all that means nothing." Indeed, Pony's presence there may suggest he's in Hong Kong for the long haul.

A version of this article appears in the July 1, 2018 issue of Fortune with the headline "Ma vs. Ma in Hong Kong: a Luxury Real Estate Rivalry."