One's a septuagenarian male politician whose verbal gaffes raise doubts over his fitness for office. The other is a septuagenarian male politician who makes so many slip-ups that the public has almost stopped taking notice.
Welcome to Joe Biden vs Donald Trump, the prospective 2020 match-up that, if nothing else, guarantees a lot of puzzlement -- and perhaps laughs.
Biden has been making verbal missteps for so many years that he spins them as just another strand to his generally affable, unpolished persona.
But at 76 and at times visibly frail, the veteran Democratic senator and party frontrunner is under ever-harsher scrutiny.
"Falling Apart: Joe Biden Delivers 9 Gaffes, Lies, and Awkward Moments in Third Primary Debate," read Friday's headline on the influential right-wing website Breitbart after the latest face-off between Democratic candidates.
While most agreed Biden had a good night, and avoided serious blunders, Breitbart's attack was far from alone.
Even the pop music website Spin weighed in, declaring that Biden at one point "sounded like he was reading randomly arranged pieces of fridge magnet poetry."
National Review, a mostly sober conservative outlet, called Biden "a Botoxed babbling brook. He is not fit to be president."
- Orange lights, cows, windmills -
If Biden bumbles, what about the man he hopes to take on -- the 73-year-old actually in the White House?
Trump, remarkably hearty for his age, suffers none of Biden's physical challenges, which recently include a dramatically bloodshot eye and an often halting manner.
Yet while Trump has physical stamina, even drawing energy from grueling press conferences and late-night TV binges, his verbal and Twitter pronouncements are if anything wackier than those of his rival.
In Thursday's primary debate, Biden became a punchline after exhorting Americans during one rambling answer to "make sure you have the record player on at night."
Only hours earlier, however, Trump made his own reference to antediluvian technology when he told reporters he'd miss the live broadcast of the Democratic debate, but "I'm going to have to have it somehow taped."
Biden took flak for his bizarre syntax, confused references and awkwardness, for example when he said about his current and former wives: "I'm married to a teacher, my deceased wife is a teacher."
But at almost the same moment, Trump was delivering a 68-minute speech to Republican legislators in Baltimore during which he caused surprise by name checking an unknown "Mike Pounce." Was it Vice President Mike Pence that he meant? Senator Mike Rounds?
And that slip-up was nothing.
Veering from the Teleprompter script to vent his hatred for renewable energy technology, Trump said energy saving light bulbs are no good because they make him "look orange."
He acted out an extended imaginary scene in which an annoyed wife asks someone called "Charlie" why their television no longer shows the Democratic debate. Switching voice to the husband, he replied: "Darling, the wind isn't blowing, the goddamn windmill stopped."
Trump then launched a meandering assault on the Democrats' "Green New Deal" plan for reimagining the entire US economy along eco-friendly lines.
Somehow this riff led him to gesturing at Kevin McCarthy, the senior Republican in the House of Representatives and a key Trump legislative ally, and comparing him to a cow.
"Kevin is just like a cow, he's just smaller," he said.
The loyal audience looked bemused but laughed anyway.
Trump seemed to realize that the joke had been peculiar. So he corrected himself -- sort of.
"I had to pick somebody for that one Kevin and I just looked at that beautiful political face of yours."
The 2020 presidential election promises plenty of humor, but not all easy to understand. Or even intentional.