Making money - ✔
Key and Trump have contrasting backgrounds, and made their millions in very different ways.
Key started from next-to-nothing, raised in a Christchurch state house by a widowed mother whose Jewish refugee grandparents fled Nazi-occupied Austria. He is now worth roughly $50 million, thanks to his days as a foreign exchange trader in Singapore and London. He says education and hard work is the way to get ahead.
Trump was raised in Queens, New York, and reportedly inherited a stake of his father Fred Trump's $200m real estate fortune. His recipe for his own success is hard work, surrounding yourself with trustworthy people, and mastering "the deal".
TPP - ✘
The two men could not be further apart on the merits of the 12-country trade pact. "The deal is insanity," Trump says. "It should not be supported and it should not be allowed to happen." He worries about China joining the TPP as a "back-door" into the US economy.
Key has championed the TPP since day one, saying a small, export-led economy won't get rich selling to itself. He says many TPP opponents don't understand what is in it. On this point, Trump agrees. "Nobody understands it," he says.
Immigration - ✘
Trump wants to put up walls at the US border, kick out illegals, and penalise US companies whose factories are offshore. He has also proposed a ban on Muslim migration and has threatened to send home Syrian refugees.
Key wants New Zealand to be open to the world. Under his watch, migration inflows to New Zealand have hit all-time highs. He has championed foreign investment and refused to limit foreign purchases of housing and farmland. His Government has taken another 200 Syrian refugees on top of the annual quota.
There is unlikely to be a meeting of minds on the use of physical structures to block the flow of people or goods.
"These people literally want me to put up a fence around New Zealand," Key has said of opponents to trade liberalisation.
Golf - ✔
Both Key and Trump are golf fanatics. Asked about New Zealand by Newshub reporter Patrick Gower, Trump's first instinct was to name-drop New Zealand golfing great Sir Bob Charles.
On the course, Trump could pose a tougher test for Key than Obama. Key's handicap is 11. Trump's handicap is believed to be 4, though he has never produced a signed scorecard. Obama's is 17. This could be why Key was reluctant to commit to a round with Trump. "Let's wait and see who wins the election first," he said this week.
Key has also set a higher bar for himself. He says a golfer's score should be lower than their age. Key is 54, Trump is 69.
Vacations - ✘
Key loves nothing better than a week off at his holiday home on the island of Maui, Hawaii. He also has a bach at Omaha, which he has offered to foreign leaders. Don't expect Trump to take up that offer. "I don't take vacations," he says. "What's the point? If you're not enjoying your work, you're in the wrong job." And besides, he only likes staying in his own luxury resorts in Miami, Scotland, and Ireland. "What do I want to sit in somebody else's resort for?"
Language - ✔
"I know words. I have all the best words," Trump says.
Key, likewise, has a few good words too. Among his own creations are "scuttlebug" instead of scuttlebutt, "textes" as the plural for text messages, and "Afghanistainians".
He also has a good turn of phrase: "I won't be Judge Judy and Executioner." On a more serious note, both men have used strikingly similar phrases to attack opponents or threats to their countries.
"They're bringing drugs. They're bringing crime. They're rapists," Trump said of Mexican immigrants.
"Some of the them are rapists, some of them are child molesters, and some of them are murderers," Key said of expat-Kiwis in Australian detention centres.
Annoying pop stars - ✔
Key's National Party upset Eminem by using a song resembling the rap superstar's Lose Yourself in an election advertisement. Key later said the song was licensed legitimately and the party had never meant to annoy the rapper.
Trump ran into the same trouble when Canadian singer Neil Young questioned his use of protest song Rockin in the Free World at the launch of Trump's presidential campaign. Trump said he bought it fair and square, before adding: "Didn't love it anyway."
Movies - ✘
Trump is a fan of vintage cinema - Citizen Kane and Gone with the Wind. "I like a lot of the old classics best. I don't see too many today, they're too computerised," he says. John Key, not so much. His favourite film is spy spoof Johnny English.