BMW M8 Competition vs Porsche 718 Cayman GT4 RS
Compare the BMW M8 Competition vs Porsche 718 Cayman GT4 RS. The Porsche 718 Cayman GT4 RS is £27,000 cheaper. The BMW M8 Competition is 0.4s quicker to 60mph. The Porsche 718 Cayman GT4 RS is more fuel efficient. Full performance, cost & ownership breakdown.
The BMW M8 Competition is priced from £135,000, powered by a 4.4L Twin-Turbo V8, producing 617 hp, with 750 Nm of torque, reaching 0-60 mph in 3s, a top speed of 190 mph, sent to the road via all-wheel drive. The Porsche 718 Cayman GT4 RS is priced from £115,000, powered by a 4.0L Flat-6, producing 493 hp, with 450 Nm of torque, reaching 0-60 mph in 3.4s, a top speed of 196 mph, sent to the road via rear-wheel drive.
The BMW M8 Competition offers a 420-litre boot, runs on petrol, returns around 23 mpg, is covered by a 3yr / unlimited mi warranty. The Porsche 718 Cayman GT4 RS offers a 125-litre boot, a usable front boot, runs on petrol, returns around 23 mpg, is covered by a 4yr / 50k mi warranty.
On cost of ownership, the Porsche 718 Cayman GT4 RS is £27,000 cheaper than its rival, the Porsche 718 Cayman GT4 RS costs less in annual maintenance (£1,500 versus £1,300), a full tank costs around £85 for the BMW M8 Competition and £70 for the Porsche 718 Cayman GT4 RS.
Driving Character: BMW M8 Competition vs Porsche 718 Cayman GT4 RS
The BMW M8 Competition defines the modern grand tourer, blending brutal 617hp twin-turbocharged V8 performance with a sophisticated M xDrive all-wheel-drive system. While it possesses the pace to dismantle almost any supercar, its 4,395lb mass remains a constant consideration, particularly through tighter, technical sequences where it lacks the nimble precision of a lighter M4. The adjustable rear-biased drivetrain allows for playful rotation, yet the chassis is primarily tuned for crushing vast distances with absolute composure. It is a formidable machine that prioritises stability and immense, exploitable torque over raw, stripped-back track feedback, representing the ultimate high-speed cruiser in the current M portfolio.
The Porsche 718 Cayman GT4 RS represents the apex of the 718 platform, transplanting a 493hp naturally aspirated flat-six from the GT3 into a mid-engine chassis. The result is a machine with staggering agility and a turn-in response that makes even the standard GT4 feel soft. The chassis balance is dominated by rear-end grip and sharp, responsive steering that provides constant feedback. It is an extreme instrument, demanding a high level of expertise to truly extract its full potential. The power delivery is frenetic, culminating in a high-revving wail that defines the car's racing-inspired character.
Head-to-head, the division is clear: the Porsche 718 Cayman GT4 RS takes our 0-100 driving character grading, 78 against 96. Characteristic of the BMW M8 Competition: Effortless, high-speed GT pace with genuine back-road ability. For the Porsche 718 Cayman GT4 RS: GT3-derived engine in the lightest, most track-focused Cayman ever. In outright terms it is 617 hp against 493 — a 124 hp gap — and the BMW M8 Competition reaches 60 mph 0.4s sooner.
Interior & Cabin: BMW M8 Competition vs Porsche 718 Cayman GT4 RS
Stepping into the M8 Competition reveals a cabin dripping in premium Merino leather and intricate carbon fibre detailing, confirming its status as a pinnacle M product. The ergonomics are quintessential BMW, featuring an intuitive, M-specific digital interface that provides all critical telemetry without overwhelming the driver. While the materials and build quality are exemplary, the two-door layout compromises access, and the rear quarters remain strictly occasional seats despite the car's generous overall proportions. It strikes a successful balance between a focused, driver-centric cockpit and the luxurious, refined ambiance expected of a high-end grand tourer, successfully isolating occupants from the road's harsher realities.
The interior is a study in weight reduction, featuring CFRP door panels, lightweight door pulls, and carbon bucket seats that lock the driver in place. The presence of the standard roll bar behind the seats signals its intent, creating a sparse, motorsport-focused atmosphere. Sound deadening is intentionally minimal, allowing the mechanical symphony—and the roar of the intake located just behind the driver's head—to flood the cabin. It is not designed for luxury or comfort, but rather as an extension of the driving experience, prioritising tactical feedback and material efficiency above all else.
Head-to-head, the division is clear: the BMW M8 Competition takes our 0-100 interior & cabin grading, 86 against 50. Characteristic of the BMW M8 Competition: Luxurious, driver-focused cabin with excellent build quality. For the Porsche 718 Cayman GT4 RS: Stripped-back, motorsport-focused cockpit.
Daily Usability: BMW M8 Competition vs Porsche 718 Cayman GT4 RS
Despite its status as a performance powerhouse, the M8 Competition remains surprisingly liveable for daily duties. The 440-litre boot provides sufficient volume for weekend escapes, though the long doors and low seating position can hinder easy egress in tight urban car parks. Comfort mode successfully softens the adaptive suspension, making motorway slogs relatively effortless, while the all-wheel-drive system ensures the car remains secure in varied UK weather conditions. Its sheer width, however, requires constant vigilance in narrow city streets, as the low-profile rubber and stiff structural setup demand care when traversing speed bumps or uneven urban asphalt.
Daily utility is significantly compromised by the track-oriented nature of the GT4 RS. The suspension is exceptionally firm, making it punishing on all but the smoothest road surfaces, and the lack of sound insulation makes it unsuitable for long, tedious commutes. Despite this, the front and rear trunks remain available for storage, and the inclusion of a front-axle lift system helps navigate urban obstacles. While it is technically possible to drive to the track, the RS experience is best reserved for spirited road use or dedicated circuit days rather than routine errands.
Head-to-head, the division is clear: the BMW M8 Competition takes our 0-100 daily usability grading, 70 against 35. Characteristic of the BMW M8 Competition: Comfortable, capable long-distance GT for daily use. For the Porsche 718 Cayman GT4 RS: Usable but clearly built for track days over commuting. that means 420 litres of boot space against 125, plus a usable front boot in the Porsche 718 Cayman GT4 RS.
Ownership: BMW M8 Competition vs Porsche 718 Cayman GT4 RS
Ownership of an M8 Competition is an exercise in managing significant operating costs, commensurate with its supercar-killing performance. The BMW dealer network offers comprehensive support, but prospective buyers should factor in the substantial expenses associated with premium tyres and high-performance brake components, which wear rapidly under enthusiastic use. While residuals have stabilised, the market for such a specific, high-output V8 GT remains relatively narrow. Annual maintenance costs are predictably high, though the car benefits from a robust community and global parts availability, ensuring that the heavy financial commitment yields a reliably formidable and well-documented performance machine.
Owning a 718 Cayman GT4 RS is a high-stakes proposition, with high purchase prices and significant service costs reflecting its status as a low-volume, specialised performance vehicle. Values have appreciated rapidly, as the model occupies a unique space in the modern Porsche lineup. Owners benefit from the comprehensive Porsche Motorsport support network, which is essential for managing RS-specific components that are more expensive and harder to source than standard parts. It is a collector's dream, provided the owner acknowledges the substantial overheads and the demanding nature of maintaining a high-performance track machine.
Head-to-head, the division is clear: the Porsche 718 Cayman GT4 RS takes our 0-100 ownership grading, 72 against 78. Characteristic of the BMW M8 Competition: Backed by strong BMW reliability reputation. For the Porsche 718 Cayman GT4 RS: Mechanically simple, Porsche-grade reliability. On the wallet the two diverge at £135,000 versus £115,000 — a £20,000 difference, with annual maintenance of £1,500 against £1,300, and warranty cover of 3yr / unlimited mi versus 4yr / 50k mi.