Whatever opinions you've already formed about the TT RS, its combination of talents is unarguably hard to find elsewhere. We're not just talking about 400hp and all-wheel drive, either. Desirable two-door coupés with a compact wheelbase and usable boot are not exactly thick on the ground. Sure, there's the BMW M2 and the Porsche 718 Cayman, but most mainstream manufacturers abandoned the segment long ago.
Consequently, one of the more affordable alternatives to the all-singing RS model is the slightly more middleweight in concept TTS. Unlike the Audi Sport version, it can still be configured to your liking, and you can expect a whole heap of change leftover for doing so. For the coupe, with the standard six-speed manual gearbox you can't have in its sibling, it starts at just over £40k - undercutting the RS's original entry-level price by a cool £11k.
Even with the optional DSG dual-clutch gearbox selected, you'll be the best part of £10k to the good. And for that you get the same 305hp EA888 2.0-litre turbocharged engine that makes the Volkswagen Golf R so relentlessly wonderful, not to mention a less aggressive styling pack that does away with the fixed spoiler and in-your-face honeycomb grille. The TT S we borrowed even came in Nano grey, a pleasant shade of incognito not available to the RS buyer. Parked next to each other, the buttoned-down look arguably does Ingolstadt's coupe a favour in the svelte department.
Sure, there are some marginal differences inside - the Alcantara has gone from the steering wheel and gearlever; the drive select and starter button have migrated back to the dashboard; some trim materials are mildly less expensive; and the Virtual Cockpit MMI system is slightly less ritzy - but it's the same basic (as in high-end) experience, and you even get the all-important adaptive Magnetic Ride dampers as standard. Unfortunately, in this instance, they came attached to optional alloy wheels no smaller than those fitted to our RS. Taking the TT S's softer suspension settings into account, the resulting brittleness reiterates what we'd long suspected: you tick the 20-inch wheel option at your own risk.
Still, the blend of amenability, pace and feigned four-pot burble is never a thread less than convincing. At lowish speeds and with run-of-the-mill throttle openings, the TT S is barely any less keen than the RS. In fact, its response to marginal inputs is probably a notch better than in its sibling despite giving away 74lb ft in torque. (Beyond the usual beat of lag, I suspect there's an economy minded accelerator pedal tune to blame for that, Audi being understandably keen for the thirsty in-line five not to rouse itself without reason.) As a result, a commuter - or anyone constrained mostly to town driving - might start to wonder what all the fuss is about. After all, 4.6 seconds to 62mph is plenty swift enough, and the same quick-shifting seven-speed DSG makes it no harder to exploit.
You'll generally be doing better than a 30mpg average too - which you won't in the RS. Eventually, though, side-by-side driving only let's you play devil's advocate for so long. Nudge the accelerator pedal an inch or three closer to the bulkhead and, like all objectively great engines, the five-pot starts rewiring the TT's appeal with each ascending 1,000rpm. Yes, it is partly about raw speed - there's no concealing the best part of 100hp at 5,800rpm - but it's also about tonality: the EA888's chirpy baritone is no match for the offbeat bawl of a 1-2-4-5-3 firing order; not at 2,500rpm, and definitely not at 6,750.
To argue the case for one while driving the other is like trying to recall the benefits of a gluten free diet while eating a kebab. And with the heavier, thirstier, revvier lump on song, the TT's chassis - that immutable, imperturbable, G-meter botherer - makes the best kind of sense. The S's own quattro-fortified setup is hardly any less able, nor any more effort to drive very quickly. But because it can't claim to be rocket-powered, its handling limit (on the public road, at any rate) seems distant to the point of detached. In the RS, the car's ironclad grip on the tarmac doesn't seem so unreasonable when you're provided with the means to test it.
Factor into this effect the implications of its model-specific tuning - a tendency to feel that bit flatter and sharper, and less obviously endowed with meaningless stiction in the steering - and the RS's settings do enough to win you over. On their own, they'd probably be insufficient to justify the enormous difference in price (a very nearly new example being virtually on par with our long termer's sticker price). More often than not though the real distance between the two is no more than half-a-litre in size. And comfortably worth every penny.
Car: 2017 Audi TT RS
Run by: Nic Cackett
On fleet since: December 2017
List price new: £50,615 (As tested £61,080 comprising £550 for Catalunya Red paint, £1,695 for 20-inch '7-spoke rotor' design alloy wheels in matt titanium-look with diamond cut finish, £325 for brake calipers in red with RS logo at the front, £895 for RS Red Design Pack, £945 for Matrix LED headlights with LED rear lights and dynamic front and rear indicators, £250 for Audi Smartphone Interface, £1,000 for RS Sport exhaust system, £995 for RS Sport suspension with Audi Magnetic Ride, £800 for electrically adjustable front seats, £800 for Matrix OLED rear lights, £325 for Audi Phone Box with wireless charging, £1,830 for on the road costs and £55 for first registration fee)
Last month at a glance: Is the TT best as an S Express?