It's been an interesting year behind the wheel here at Cars Technica. Quite a few of the cars I've tested have delivered surprises—underwhelming ones in the case of best-sellers like the Toyota Camry and Nissan Rogue, as well as unexpectedly delightful ones like the Kia Niro and Honda Accord. Think of today's story as a microcosm, then. It's about two cars from the same OEM, built on the same architecture, similar enough to be cross-shopped. The brand is Audi, the cars are the 2018 A4 sedan and 2018 S5 Sportback, and the surprise? For that you'll have to read on.

Neither car is a stranger to these pages. We first drove the A4 sedan back in 2016 at its launch, proclaiming it "for nerds, by nerds." Our first taste of the more powerful, more expensive S4 sedan and S5 coupe came a year later, as did our first drive of the Sportback, a sleeker, yet practical, five-door alternative to the sedans. First drives are certainly informative, but you'll learn a lot more living with a car for a week than you will sharing it for the day with another auto journalist. And over the summer, I had the opportunity to really get to know these four-ringed siblings.

The car I thought I'd love

OK, that subheading gives the game away, but it's true: I did think the S5 would be the one I'd love. After all, it's a Sportback—the name Audi gives to its five-door fastback sedans. My love for the five-door body style is well documented at this point; I spent my own money on a Saab 9-2x , and I'm a true believer that five door wagons, hatches, and fastbacks really do offer the most practicality while also looking better than almost anything else on the road.

The July 4th weekend and the annual IMSA Six Hours of the Glen endurance race at Watkins Glen in upstate New York proved to be the perfect test of the S5 Sportback's practicality. With the rear seats folded flat, the Audi easily swallowed assorted camping paraphernalia, and, despite the lack of adaptive cruise control, the 400-mile journey north was far from a chore. The front seats were comfy, the adaptive sports suspension cosseted us when the tarmac turned poor, and if you must have a red leather interior, this particular one (called Magma Red in Audi-speak) looked classy and not at all like the workplace of a person of negotiable affection.

But the longer I spent admiring the S5—hard not to do when it was parked next to the tent—the less I liked the shape. From the rear, I'm still a fan, but there's something about the hood line and the way it curves back down toward the A pillar that gives the car an air of bulbosity. This might be color sensitive; I don't notice the same effect on S5 Sportbacks painted in darker metallic tones. Looks are subjective and all that, but when a car's looks are part of its USP (unique selling proposition in car-speak) and those looks fall a bit flat, it's a turn off. In the Sportback's defense, it did generate a lot of positive attention from passers-by, so perhaps I'm alone on this.

The other USP for the S5 Sportback (and this applies to the coupe, too) is that the more powerful turbocharged 3.0L V6 engine and uprated running gear should be more exciting to drive. With 354hp (260kW) and 369ft-lbs (500Nm) it is indeed more potent than the 2.0L in the regular A4 and A5, and it will reach 60mph from a tollbooth more than a second earlier than the four-cylinder model. But despite a more rear-biased all-wheel drive system and the (optional) Audi Sport rear differential—a torque-vectoring unit no less—it's actually not that engaging to drive. This confirmed something we noticed in 2017 at the S5 launch; despite being smaller and a bit lighter than the S4 sedan, it was the latter that was more fun when the road turned curvy.

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

The car I didn't expect to love

I wasn't actually even supposed to drive the A4. Originally, the company that manages one of the local press fleets had scheduled a week with a Dodge Challenger Scat Pack, which I was to pick up at Dulles International Airport (saving Ars a cab fare and therefore killing two birds with one vehicle, as it were). Something evidently happened to that slice of four-wheeled Americana, because in its place was the blue A4 you see in the gallery above. Like the S5 Sportback, it was well-used for a press car, having recently nudged past 10,000 miles.

Imagine my surprise when I discovered that this particular A4 came with three pedals. I've stood up for the automatic transmission, and the auto 'box that Audi uses—ZF's 8HP eight-speed—is the best in the business. (I swear you'll be able to read a feature on this mechanical marvel at this very website, eventually.) But after a few days spent with the stick shift version, I couldn't escape the fact that it was just more engaging to drive than any other A4, S4, A5, or S5 I've tried. The clutch action was nice and light, yet positive, and the engine's stop-start system also provides an anti-stall function that should save the novice any embarrassing moments.

The A4's fun factor was helped by the fact that it came with the Sport plus package. That means the same thin-rimmed three-spoke steering wheel, some sportier suspension that's 0.9 inches (23mm) lower than normal, and some other bits and bobs that lift the interior into the same league as the more expensive S* models. It's obviously slower than the V6-powered car, with just 252hp (185kW) and 273lb-ft (370Nm) on tap, but it never feels slow or underpowered.

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

Jonathan Gitlin

The A4 has it

The A4 also featured a new driver aid that right now is exclusive to Audi, and one that only works in a handful of cities. It's called Traffic Light Information , and it lets the car communicate with stop lights to tell you how long you have to wait for the signal to change. It's not a feature to change one's life, and yes, you can usually get a countdown to green by watching the pedestrian sign. But I must confess I found it rather convenient, more so when it told me how long a light was going to stay green—when it was working, at any rate. Although the District of Columbia is one of the 10 cities where Traffic Light Information is operational, it didn't work at every traffic light, or even consistently (i.e. sometimes it would work for a light, then fail some time later at the same light).

By the end of my week with the manual A4, the conclusion was inescapable. I found the A4 more engaging to drive, just as nice to sit in, and almost as practical as its sportier stablemate. And that's before we've talked about the respective prices.

The MSRP on the A4 in the mid-level Premium Plus trim is $43,700, and our test car tipped the scale at $51,650 (for the Sport plus package, its blue paint, and the Navigation and Telematics package that gets you Virtual Cockpit). The S5 doesn't even get out of bed for less than $54,400, and once you add up the options—Navigation, S Sport package, plus some other bits and bobs—the S5's sticker was a hefty $63,975. On top of that, the stick shift A4 drinks less gas, with a combined 27mpg versus 24mpg for the S5.

Less isn't always more in the automotive world—the four-cylinder Kia Stinger isn't as good as the V6 model, for instance. But in this case, the cheaper, slower, less powerful Audi is the one I'd pick, particularly when it comes with a manual transmission. That makes it all the more upsetting to know that unless you act fast, you'll never get to try it for yourself. Thanks to a worldwide lack of demand, Audi is dropping the manual transmission entirely for the A4 and A5 from the 2019 model year onwards. Insert sad face emoji here.