Both models represent best-sellers in their respective makers' range and can trace their history back more than 30 years. So with the release of an all-new BMW and revised A4, it looks like this is one fight that just got a whole lot tougher.
Code-named F30, the new 3 Series promises to be better than the model that came before, in every single area. And considering that the current generation isn't exactly struggling to shine against newer competition, that's a big claim. Not only is there a new look, inside and out, and a line-up of new engine and chassis options, but there's also even a range of trim levels (called lines) that promise to make the new 3 more individual than before.
But despite all of these newsworthy changes, Audi is aiming to land a sucker punch with its recently revised A4. The changes aren't nearly as extensive, but a raft of visual and mechanical updates makes the saloon an even stronger competitor.
Catch sight of the 3 Series and it's clear that it's all change for the exterior design. Sure the inspiration (5 and 7 Series) is there for all to see, and it's obvious where this car slots into the line-up, but the front end, in particular, demonstrates a powerful new direction. The double kidney grilles are intersected by the headlights, and sit proud of the bodywork, and though most models share similar bumper and air dam layouts, different treatment to the plastic and bright work areas on each "line" shows a subtly different face.
There's not nearly so much going on with the Audi but, like the best fighters, it's emerged through the three years since its launch with a comparatively fresh face. It still looks classy and understated, but now uses the same grille and headlight treatment found on the newest A6.
One area where the new 3 Series really has to make its mark is with cabin space - too often the old model fell short against its competition. And with a 50mm increase in wheelbase, most of which translates into extra rear legroom, there's almost nothing to separate the pair in terms of room or comfort across the rear bench.
There's little between them up front as well, and both demonstrate just how to construct a quality cabin, albeit in subtly different ways. Like the metalwork, the Audi hasn't changed much, which means a sober but driver-focused environment with clear instruments, a high transmission tunnel and high-tech feel to the equipment. On the other hand, it's clear the 3 Series has taken its direction from the latest 1 and 6 Series, resulting in a busier but still high-quality layout.
It's not the way these cars look, or even feel when sat inside them, that really matters though; it's what happens when you turn the key that counts. And this is where the big news is in the BMW - the latest 3 Series features some of the brand's latest engine technology. The six-cylinder 335i remains, albeit with some minor tweaks for improved economy and efficiency, but it's the turbocharged 2.0L four-cylinder engines that make the biggest impact - especially the 328i.
The most powerful of a pair, the 245hp unit, utilises TwinPower turbo technology (a variable vane charger) to offer 350Nm at only 1,250rpm. Along with the Precision Direct Injection, Double-Vanos variable camshaft timing and VALVETRONIC valve timing it makes for an incredibly flexible unit. Deploy all of that power from a standstill and the saloon will sprint from 0 to 100kph in only 6.1 seconds. Sure it doesn't sound as melodious as its bigger brother, missing that straight-six snarl at the top of its rev range, but a number of innovations have been applied to ensure it remains refined. A dual-mass flywheel and a pair of balancer shafts fitted at different heights result in a smooth and almost vibration-free lump and the 328i spins freely and fiercely all the way to the red line.
In reality, there's no engine in the Audi range that can truly match it - the most powerful 2.0L four-cylinder unit in the A4 only commands 211hp. The next step in the petrol range leapfrogs to the 3.0L V6 in the S4, which boasts 333hp and is both more expensive and sportier in character than the 328i Sport. However, despite the Audi giving away 34hp to the BMW, the torque figures are exactly the same, which is why the A4 still manages to complete the 0 to 100kph dash in 6.5 seconds, only 0.4 seconds behind its rival.
One of the key reasons for the BMW being quicker is the new eight-speed automatic transmission that is now available across the 3 Series line-up - the A4 "makes do" with only seven ratios. Not only does it boast an extra cog over its competitor, but when in automatic or manual mode it proves more intuitive and quicker to react to the driver's demands. Specify the paddle shifters behind the wheel and each upshift is a tactile delight, hammering home the next gear with barely a pause in acceleration - especially in Sport mode.
That's not to say the S-Tronic system found in the Audi is a disappointment - after all, it's still smooth and quick shifting and, frankly, seven gears should be enough for anyone. Indeed, if it wasn't for the changing position of the rev counter's needle, you'd be hard pushed to tell that it ever changed ratios. But a bit like the rest of the package, when you want it to be sharp and react to your inputs on time, it doesn't quite cut it.
Another area where the A4 shows its comparative weakness is on a flowing open road. There's plenty of grip on offer (especially when fitted with the firm's famed quattro four-wheel drive system), but it feels like a blunt uppercut next to the scalpel sharp left-right jab of the BMW. There's no real body roll to be detected, and you can certainly lean on the car's chassis, but for all its dancing around the ring, it just can't communicate like the 3 Series.
In comparison, attack an apex in the BMW and things are very different - not only does the rear-wheel drive set-up offer as much grip as the front-wheel drive Audi, but it assaults your senses as it does so. There's a delicate balance to the chassis that communicates everything going on beneath the wheels and with every input to the steering, throttle or brakes, there's a resulting message to the hands, hips and head. But for all this communication, you could expect the hard-hitting BMW to suffer when the going gets tough - as every 3 Series so far has come with a reputation for a stiff ride and unforgiving run-flat rubber. Truth is, the new 3 Series demonstrates the best ride and handling balance we've seen - only the occasional pothole catching the suspension out as the wheel drops into the void.
Of course, that is likely to be down to the generous specification of the launch cars, which all featured Dynamic Damper Control and variable ratio steering. We can't be sure that the passive set-up, which is likely to be found on many 3 Series, will make it quite as capable an all-rounder. Still, within Driver Performance Control (DPC), the throttle, engine and steering response, as well as the level of intervention offered by the Dynamic Stability Control (DSC) can all be altered to suit individual preference. For those so equipped, the DPC will also alter the parameters of the automatic gearbox, servotronic steering and Dynamic Damper Control.
BMW isn't alone in offering such a system though; Audi A4 buyers can benefit from the company's Drive Select, which changes the way the accelerator, automatic transmission, power steering and even the climate control behave. There's also the option of specifying an upgraded system that can control the sport differential, adaptive cruise control, dynamic steering and damper control settings.
As expected, both the A4 and 3 Series are more efficient than their predecessors. The 328i comes with BMW's new ECO Pro mode, a system that uses a visual display to not only warn drivers if they are pushing too hard on the accelerator, but also how many kilometres they have added to the car's expected range when following the instructions. Like the 328i, the A4 benefits from a stop-start system, energy recuperation and direct injection, and the Drive Select can be set to efficiency mode to make the most of the fuel used.
But of course, it's how these cars perform as a package that matters and, as expected, there isn't much that catches either of them out. Despite many expecting this to be one bout that is more fiercely contested than before, with the winner settled on points alone, just five minutes behind the wheel of the new 3 Series will reveal it's a knockout victory in the BMW's favour.
Price, base N/A
Engine 2.0L inline four, turbocharged
Gearbox Eight-speed automatic
Power 245hp @ 5,000rpm
Torque 350Nm @ 1,250rpm
Fuel economy, combined 6.3L/100km
Audi A4 2.0L SE
Price, base N/A
Engine 2.0L inline four, turbocharged
Gearbox Seven-speed automatic
Power 211hp @ 4,300rpm
Torque 350Nm @ 1,500rpm
Fuel economy, combined 6.3L/100km