The Audi Q7 was the most important new mainstream production car to be launched at the Detroit Auto Show, joining a growing throng of recently refreshed big SUVs. Given that BMW debuted a new X5 in 2014 (although it looks just like the old one), Volvo has finally launched a new XC90 (which is highly impressive) and Mercedes is refreshing its largest SUV (renaming it GLS to fit with its saloon car name strategy), the Q7 needs to be good.

The last Q7 had a bit of a reputation as a bit of a bruiser. Physically massive, heavy, and likely to be found five inches from your bumper travelling up the M4, you didn't want to mess with the Q7. Aware of some of these issues and that they put off some potential buyers, Audi (and parent company VW) set out to create a large SUV platform that offered the same level of interior accommodation and better tech features, but within a more compact vehicle that is several hundred kilos lighter than before.

Job done then, because the new Q7 weighs 325kg less than the old and achieves around 25 per cent better fuel economy model for model. It is shorter and narrower than before too. But Audi says it offers more space inside. Is it all too good to be true?

Well, you might think so when you look at the exterior design. Like 'em or loathe 'em, it's been hard to quibble with the quality of any Audi design in – oh, about the last twenty years. Yes they might look aggressive, and they might look the same as one another, but they also have impeccably surfaced sheet metal, tiny panel gaps, are beautifully detailed and have a timeless quality that means they look smart and special just about anywhere in the world. Big grille aside, Audi design tends to be characterised by as few and as simple lines as possible and then some super-expensive details.

The new Q7 isn't like this. It looks awkward. Making it more compact makes the first glance of it conclude that it's a large estate car rather than an SUV. That'll be good news as far as some are concerned, but walk around to the front and you'll find a new, rather bulbous, difficult interpretation of the Audi front grille which looks like it's been grafted on.

The busy lines all over the apertures and surfaces are un-Audi-like too. And on the body side there are various surface changes and fussy elements that just aren't befitting of the brand's design language. And somehow, despite wearing 21-inch rims, the wheels on the blue car in Detroit managed to look small. Imagine it on the standard 19-inchers.

We know some think design is subjective, but the Q7 really isn't a looker. Every non-Audi designer we spoke to in Detroit thought the same. But interestingly, it's the work of the now-departed design chief. So it doesn't represent where Audi's going. The Prologue concept shown in LA represents the future, and thankfully looks way better. For plenty of people as long as there are those four rings on the front, the exterior looks won't matter - but the Q7 feels like an exception.

Where Audis really come alive is inside. It's here the new Q7 doesn't disappoint, with the 12-inch TFT fully digital gauge pack first seen in the TT, which can be supplemented with a head-up display if you like. Then you get Audi's super-slim centre screen display, which motors silently out of the dashboard from its stowed position and is controlled by the familiar MMI rotary controls.

Those knobs and switches are augmented by Audi's next generation MMI touchpad, allowing for handwriting and gestural inputs. Best of all, the Q7 will be able to run both Apple CarPlay and Android Auto from the get-go and it runs all of the displays via the latest NVIDIA Tegra 4 Processors – ensuring super-fast response to inputs and beautifully rendered screen graphics.

Add its matrix LED headlamps, optional Bang & Olufsen sound system (which is over £6K), the ability to isofix in six childseats, electrically-dropping rear seats, multi-zone air-conditioning, next-generation "natural speech recognition software" (ask it things like "where can I get fuel from nearby?"), access to the Google Play store, and a tech list that's so long we'd need three more articles to detail it all, if it's the most hi-tech SUV on the market you want, there's likely to be little to touch the Q7.

So the tech's lovely, but what of accommodation for the passengers in the second and third rows? Well in row two, you'll likely be happy – with plenty of space and various rear seat entertainment options – but in the packaging of this car, Audi has dropped the ball when it comes to the third row of seats. Because the Q7 has been designed to accommodate the e-tron Quattro electric drivetrain, the batteries sit over the rear axle. The net result is the two rearmost seats can only really accommodate kids at best. Gangly teenagers will struggle to get in (or more likely moan). Fully grown adults most definitely should not try to get back there (believe us, we tried, the results were not pretty).

So if you need true space for 7, as the very name of the Audi suggests, then you'll not be likely to succeed. A better path would be to opt for a Volvo XC90. And it's against that rather formidable opposition that the Q7's case starts to come undone a little.

With the rather large proviso that we haven't driven either car yet, the Volvo manages to be far more spacious inside, looks better on the outside and is now a match for Audi in terms of both interior material appointment and tech. It's likely to be cheaper to buy, too. Audi counters by giving the option of V6 TDi engines (the Volvo's are all four cylinder), that lightweight body and theoretically good fuel economy. But you'd also have to bear looking at it every day, and that's the hurdle we just can't get over with the Q7.