A flagship's role is to stand as the pinnacle of an automaker's greatest efforts to date. It has to offer the best of what the automaker itself offers, with cost not factoring as much into the equation. The Cadillac CT6... sort of falls into that category. (Some say it's the Escalade, but that's up for debate.)

Indeed, the CT6 scoops up most of Cadillac's latest technology, whether it's the semi-autonomous Super Cruise, four-wheel steering or, in the case of this review, a big ol' plug-in hybrid battery. But this full-size luxury sedan isn't exactly built to compete with the flagships from Audi, BMW and Mercedes-Benz.

Instead, the CT6 carves its own path. By cutting back in small but perceptible ways, the CT6 presents itself as more of a value buy -- especially so with the plug-in hybrid. It brings a lot to the table, and while it may not have the wow factor of its more expensive rivals, it's still a compelling car.

Under the radar, inside and out

Cadillac's biggest sedan is decidedly subtle. There are no flashy exterior cues, just some interesting shapes in the headlights (the running lights resemble teardrop prison tattoos -- in a good way) and some clever chrome accents on the taillights out back. I'm not a fan of the reverse lights being tucked into the bottom of the bumper, which is not easy for taller cars to see. Cadillac also has this thing where the size of the wheels is only barely proportional to the massive body around it -- I noted this in my CTS V-Sport review from last year, as well.

The interior doesn't pack S-Class quality, but it's nice. The CT6 is a large luxury car, so space is ample for both front and rear occupants, and the lucky ones in the back get to enjoy a standard rear entertainment system. My tester's black-on-black-on-black-on-black leather interior feels cavernous, and materials on the dash and center console only feel slightly worthy of the $70,000-plus price tag. This is where the car falters most against its competitors.

Light pouring in through the big windows and dual panoramic moonroof help break up the interior's darkness, but a high rear beltline eats into visibility through the rearview mirror. And speaking of mirrors, can somebody tell Cadillac to give up on the tiny-side-mirror trend? For such a big car, the CT6 has hilariously small side mirrors, which are just plain bad for rearward visibility.

The PHEV system's battery lives in the trunk, so instead of the standard CT6's 15 cubic feet, you're stuck making do with just 11. That limits what you can put in the trunk, but golf clubs and suitcases will still fit, just not all at once. If you're not planning any long trips, it handles weekly grocery duties just fine.

Enlarge Image Nick Miotke/Roadshow

Hush, hush

While it may lack the visual panache of its more expensive tablemates, the CT6 Plug-In does offer a quiet ride. Cadillac's noise isolation is solid, and when operating on EV power alone, the cabin remains hushed. Some of that credit goes to the Goodyear Eagle Sport all-season tires, which have thick sidewalls (235/50 front, 265/45 rear) that don't get noisy until the upper end of highway speeds.

The CT6 drives on the European side of soft, which is to say it's not pillow-soft like a Lexus, but closer to the firm, composed feeling you get from German executive sedans. Potholes and other road hazards are easily dispatched and only barely translated to the cabin, again partly owing to the thicker soles on the Caddy's shoes.

The plug-in powertrain puts out a commendable 335 horsepower and 432 pound-feet of torque. It'll hustle nicely on electric power alone, and keeps the momentum when the 2.0-liter four-cylinder gas engine kicks in. The transmission is a complex mess of planetary gears and clutches with multiple variable and fixed gear ratios, but in layman's terms, it basically acts like a CVT. It occasionally exhibits weird tendencies: sometimes the gas engine kicks in and immediately revs high and loud. And when you're operating largely on gas-engine power, you get a lengthy delay between pushing the pedal and feeling the acceleration.

If you want to maximize your efficiency, slapping the shifter to M starts up a four-stage regenerative braking system. You can "downshift" through increasingly strong levels of brake regen to stop smoothly, or you can put it right into its strongest setting and get 99 percent of the way to one-pedal driving. Frequent use of the regenerative braking won't add a ton of range, but every little bit helps, and trying to one-pedal down the road makes things a bit more exciting if you're a raging nerd like I am.

The CT6 Plug-In's sizable battery gives it a 31-mile EV range that's totally plausible in temperate climates. But that range was closer to 25-27 miles when I tested it in a chilly Michigan February, and you'll lose about a mile of range overnight if the car isn't plugged in. The CT6 will do an impressive 78 mph on electrons alone, but that big battery also lends to big charge times -- nearly 4.5 hours on a Level 2 charger. Over a couple hundred miles of mixed use, displayed MPG hovered around 31. There's a mode to hold the battery charge at a given level while driving -- like if you're on the highway and want to save your electricity for around-town stuff -- but it needs to be selected each time the car starts, so don't forget.

Enlarge Image Nick Miotke/Roadshow

Tech that could be better

Here's the real bummer -- you can't get Cadillac's excellent semi-autonomous Super Cruise system with the CT6 Plug-In. Super Cruise works in conjunction with the CT6's four-wheel-steering system, which isn't fitted to this model due to PHEV packaging constraints. So you're stuck with more traditional driver-assist systems.

Those systems work fine, though. Adaptive cruise control is smooth, but the forward collision warning is a bit touchy even on its least anticipatory setting, especially when you're trying to maximize brake regeneration.

The CT6 Plug-In also lacks the latest iteration of Cadillac's CUE infotainment system. It's still plenty powerful, with a new slate of connected apps and a standard 4G LTE Wi-Fi hotspot. But since this is the company's flagship, Cadillac should have brought its new system over here. I do like the extra hybrid-only pages in the infotainment system, which lets me plot out charging strategies and see how the power is being routed in real time. Apple CarPlay and Android Auto are here, too, and they're as good as usual.

The configurable gauge cluster offers different layouts, all of which attempt to offer up as much simultaneous information as possible, which is great for preventing distracting looks at the infotainment screen. The USB ports charge fine and are ample in quantity, although the under-seat location of those ports in the rear aren't immediately obvious, and might cause consternation when you're riding three-up in the back.

Enlarge Image Nick Miotke/Roadshow

How I'd spec it

The CT6 Plug-In is only available in a single specification with a whole bunch of standard equipment, so I guess that's how I'd spec it, because I don't really have a choice. If I had the option, I'd add Super Cruise for a few thousand extra. But I can't. Standard equipment includes forward and reverse autobrake, a panoramic moonroof, a head-up display, a 360-degree camera system and parking sensors.

Down to brass tacks

Cadillac's big-boy PHEV will set you back a cool $76,090 including $995 for destination. That sounds expensive until you realize that a comparably equipped BMW 730e iPerformance costs nearly $15,000 more. The outgoing Mercedes-Benz S550e -- a refreshed version is coming soon -- has an even larger price disparity. The Cadillac's closest competitor is the 2018 Lexus LS 500h, but even that one is still about $4,000 more expensive. None of the aforementioned cars offer the same level of standard equipment, either.

So the CT6 Plug-In is, in fact, a value proposition. Sure, it may not be able to hold a candle to the 7 Series' driving dynamics, it's nowhere near as fancy as the S-Class and nowhere near as pretty as the Lexus. But if you're willing to accept those sacrifices, you'll end up with a subtle plug-in hybrid that offers excellent range, tons of interior space and a ride that's pretty darn Germanic. If this is your shopping segment, the CT6 Plug-In is definitely worth your time.