Hmm..
He's smoking the good stuff if he thinks the Insight is a big car with no interior space. The Insight is a small car with no interior space.

Nobody in their right mind would consider the Insight big, it's a tiny 1800lb two seater car with a 76HP engine.
They're capable of getting
spectacular mileage on the highway, but their in-city milage is still good; you would expect at least 50MPG city. He's backwards; the only time the electric motor really helps is when you are in town. It doesn't do much of anything on the open highway.
They are a cult car. Their prices are higher than they should be because of their spectacular mileage. Their prices tend to follow gas prices; with gas prices on the rise, so are Insight prices.
You don't need to spend 9k on one if you keep your eye out. That would be for a flawless, low mileage specimen. FWIW, we have $4000 into Insight #2, but I acknowledge that we got a good deal on it. I just pulled a 89.0MPG 51 mile round trip in it last weekend. Not bad for 443,000 miles.
They are not fussy to work on. They're one of the easiest modern cars I've ever had the pleasure of wrenching on. There is a surprising amount of room in the engine bay for such a small, modern car.
There is nothing that compares to the Insight fuel economy wise. It really just depends on what you need and want.
So, what do you need/want?
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Insight #1 - Silver '01 5MT @
158,388 as of 7/11 - Best Tank: 84.5MPG over 807mi

Insight #2 - Silver '01 5MT @
450,000 as of 1/12 - Best Tank: 86.0MPG over 800mi

Insight #3 - Silver '00 5MT, MIMA #163P, BCM Gauge, OBDIIC&C Gauge, BetterBattery @
228,869 as of 1/12 - Best Tank: 78.4mpg over 687mi