Earlier quoted context omitted.
I'm not sure what you're purporting to show other than two people disagreeing with each other, without providing evidence... Sure, an individual subway car has "more capacity," but does a subway system have more capacity? For example, I rarely see BART trains come within five minutes of each other. A tunnel that allows cars within 10 seconds of each other could provide more capacity than a tunnel with higher-density…
This is already a solved problem. BART may have huge headways, but Vancouver's fully automated Skytrain can run at 75 second headways (!!!). There is no universe where an SUV holding 4 people is more space efficient than a Skytrain car.
And how expensive was it to build the train? If you can build 3x the tunnels for AVs as you can train tunnels and trains for the same price, actual throughput dollar-for-dollar in infra spend would be much better with Boring Co tunnels.
Update with data: it cost $2 billion to build 50 miles of Skytrain. Apparently this prototype Boring Co tunnel cost $10 million per mile. That's a 4x cost advantage for Boring Co mile-for-mile, and I imagine they'll try to strengthen that advantage even further; after all, that's their whole company's purpose: cheap, efficient boring.