They're two high-volume plug-in hybrids, but they take different approaches to energy efficiency.

The Toyota Prius Prime, new for 2017, is the plug-in version of the world's best-known, and best-selling, hybrid car.

The 2017 Chevy Volt was new last year, a greatly improved version of the pioneering range-extended electric car.

They're now going head to head in the expanding market for cars with plugs, but how do they match up?

Both cars are compact five-door hatchbacks with designs that work hard to be highly aerodynamic. But the executions differ a lot.

The Prius Prime is the newer of the two. Most onlookers think it's a visual improvement on the regular Prius hybrid that spawned it.

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The plug-in Prius has a new and more aggressive front end, horizontal taillights—rather than the bizarre vertical shapes of the base Prius—and a large tablet-style touchscreen display inside most models.

Now in its second year, the Volt remains a sleek, low, racy shape, with a more conventional but good-looking interior.

2017 Chevrolet Volt

While the Prius is strictly a four-seater, the Volt offers a fifth seating position, though it means perching on the padded battery hump. It's not suited for anything beyond very short trips.

The Prius powertrain puts out 121 horsepower, and the EPA rates it at 25 miles of range, which we think it should deliver in most cases.

That comes from an 8.8-kilowatt-hour battery pack that sits under the rear seat and load bay.

CHECK OUT: 2016 Chevrolet Volt First Drive: Plug-In Hybrid Home Run

The Volt is quicker on pretty much every acceleration measure, with 149 horsepower, and it gets a 53-mile rating from its 18.4-kwh battery.

But the Prius Prime wins on fuel economy once the battery is depleted, at a combined 54 mpg against the Volt's 42 mpg.

Either rating, of course, is better than all but a handful of other vehicles you can buy this year.

2017 Toyota Prius Prime Premium

Behind the wheel, the new Prius Prime is a vastly better car than its predecessor.

Both of the newest Prius versions are no longer as numb and remote to drive as they have been.

The Prime is less Prius-y, more like a regular car. Most important, though, the product engineers made a critical choice.

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The Prime defaults to all-electric mode if there's any battery capacity, and doesn't turn on the engine at all until that's gone.

That's very different than the first plug-in Prius, which had such limited electric capability that drivers complained it would kick on the engine if they breathed too hard.

Because it's all-electric by default, the Prius Prime driving experience is now much like that of the Volt.

It's not as fast, and it won't go as far, but it's got adequate power up to speeds of 75 mph.

Its electric-only driving gives the same calm, quiet, pleasant driving experience.

2017 Chevrolet Volt

And with 25 miles of range, Prius Prime drivers might be able to use electricity alone for a majority of their trips—as many Volt drivers do.

The Volt starts at around $34,000, while the base Prius Prime opens at about $28,000.

The $6,000 difference, however, is halved by the Volt's federal income-tax credit of $7,500, against $4,500 for the Prime.

ALSO READ: Chevrolet Volt: Green Car Reports' Best Car To Buy 2016

So there you have it: a pair of plug-in hybrid hatchbacks with longer ranges and more amenities than before, each a better car than it was.

Which one is best for you depends on what you prioritize.

2017 Toyota Prius Prime Premium

Do you want maximum electric range? The Volt wins, at 53 miles versus the Prius Prime's 25.

Or do you want the highest fuel economy plus the longest distance between fill-ups? There, the Prius Prime wins.

The choice is yours.

And choice is good.

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