The battle of the BMWs: M550i xDrive and the Alpina B5 Bi-Turbo

W hen it comes to seriously fast, tweaked saloons, Munich has long been the home of segment-leading successes. BMW's in-house M performance division has been most celebrated for creating the M3, with the M5 not far behind, both of which have been leaving much fancier-looking motors in their collective wakes since the mid-1980s. In BMW’s seemingly ever-expanding family, however, the M5 isn’t the only option if you want a steroidal 5 Series with pace to burn. And both of the cars that we have driven will push their more-famed sibling more or less all the way – in some regards, even beat the original at its own game. Say hello to the M550i xDrive and the Alpina B5 Bi-Turbo. Indeed, in the case of the Alpina, should you find yourself on an Autobahn, a vacant racetrack or a particularly long stretch of private road, it will hit a higher top speed than the M5, thanks to its lack of electronic limiter. The B5's top mark? A serious 330kph, which is about 25kph more than you will manage in its hamstrung contemporary. If the M5 is a gentleman fighter, the B5 has its gloves off and is brawling bare-knuckle boxer. Not that you would know that from inside its cabin, which pointedly ups the 5 Series's executive luxury levels to somewhere in the upper echelons of in-car comfort, not least in the quilted Nappa leather seats. At night, the cabin is bathed in futuristic tones. A vortex-shaped light show emerg es from the door speakers, with the glow reflected from half a tree's worth of wood around the interior. That said, in its own way, the M550i is a truer sporting proposition, with a more pared-down, dual-tone approach inside, rather than ostentatious displays of wealth. It is an expensive sports shoe to the Alpina's tailor-made loafer. Upgraded suspension on the B5 gives a better ride and sharper handling, a double whammy that means you can float over bumpy roads with the same confidence that you can lean into tasty corners, with satisfyingly meaty brake improvements versus the “normal” 5 Series. When it comes to sprint credentials, the M550i can’t quite keep pace with the B5, taking an additional half a second to complete the 0-to-100kph dash, compared to the latter’s rather handy 3.5 seconds, although both will, on paper, be pipped by the M5. And while all three are powered by 4.4-litre V8s, the B5’s tuning means that it has significantly superior figures, producing 608hp (versus 456hp in the M550i) and 800Nm of torque (650Nm in the M550i). To put that in perspective, the most recent car that I have driven in that upper ballpark is the Ferrari Portofino. The B5 is much more than the suit-wearer’s car for the commute that its base building blocks represent, then. It is hardly a street sleeper, though, capitalising on the 5 Series's bullish nose with a body kit that ripples with muscular intent, decorated along its flanks with Tron -esque circuit-board lines that lead you to a rear that bristles with double twin exhausts. The M550i is a touch more subtle, although low-profile tyres and lowered suspension will give the game away to those paying close attention. In the M550, that xDrive designation signifies all-wheel drive, a system that is also exploited by the B5, distributing power between front and back wheels to keep traction and control steady. Both cars certainly feel sure-footed, although perhaps unsurprisingly the Alpina edges ahead in that particular battle. The cleverest technology is shared by the pair: the active front grille features moving slats that will either enable increased air intake or close for better aerodynamics, depending on requirements. And while I only get to test the B5's self-parking ability, operated from the key fob, it is a useful addition if you live or work in a building with tight bays. It feels unnatural and is a little nerve-racking for the first few attempts, but your confidence grows in time, even if passers-by will probably continue to look at you as if you have lost a good deal of your marbles. If finances were a trifling concern – a life goal that I haven’t quite managed yet – then the decision would be a no-brainer: B5 all the way. But for Dh155,000 less, the M550i (Dh502,750) still packs enough of a punch to make it a proper contender in this middleweight battle. And in the real world, it will do everything you realistically require of an angry 5 Series, albeit in slightly less high-level comfort as the Alpina. Naturally, if money really isn’t a problem, buy both, use the M550i from Sunday to Thursday, then crack out the B5 at the weekend for some additional thrills. Either way, who needs an M5? ________________ Read more: Latest from The National's Motoring section ________________

The battle of the BMWs: M550i xDrive and the Alpina B5 Bi-Turbo

Adam Workman says neither the M550i or Alpina B5 will leave you bored or short-changed