For car enthusiasts, the new 2018 BMW M5's spec sheet boasts a couple of disturbing items. In place of the previous car's dual-clutch and manual transmissions is an eight-speed automatic in the sixth iteration of Bimmer's midsize performance sedan. The other eye raiser is all-wheel drive tagging in for rear-wheel drive.

M5 product manager Steffen Leppert says the driving force behind the changes was feedback from owners of the outgoing car. An overwhelming number wanted a smoother operating machine claiming the dual-clutch was too jerky for normal driving. Many also wished for a more efficient way of getting power to the ground. The complaints led the development team to the adoption of an auto trans and all-wheel drive for 2018.

On tight, winding roads north of Estoril, Portugal, the new M5 goes about its business in a more buttoned up manner. Launches are buttery smooth with the torque converter automatic, and getting the 600 horsepower and 553 pound-feet of torque down from the 4.4-liter twin-turbocharged V8 isn't an issue with the M xDrive system.

The reworked engine betters its predecessor with 40 additional horsepower and 53 pound-feet more twist, helping to shove the M5 to 60 mph in 3.2 seconds. That's a smidge swifter than the 3.3-seconds Mercedes-AMG claims for the E63 S. EPA fuel economy figures aren't available yet for the new drivetrain pairing, but BMW officials says it will better the 14 mpg city and 20 mpg highway ratings the old car got with the dual-clutch.

Something that will be familiar to owners of previous M5s is the numerous adjustment options to tailor the car's behavior to their liking. The center console is littered with buttons for changing the performance of the engine, gearbox, adaptive suspension and steering that all have three settings ranging from milder to wilder. When finding combinations that suit you, red steering wheel buttons let you save two setups to call up immediately.

For the street, the middle Sport mode for the engine, suspension and steering is the sweet spot for a pleasing balance between dynamic performance and comfort. Throttle response isn't too hyper and steering has minimal play on center before tightening up with satisfying heft tuned into the wheel. The suspension and Pirelli P Zero tires return great stick rounding corners, while sufficient damping is still available to take the edge off of impacts.

For relaxing trots, the engine's Efficient mode and Comfort for the suspension and steering are excellent. Engine response is quick enough, the chassis doesn't flop around bends and steering is still responsive with some weight in the wheel. Calling up Sport Plus for all the systems are a little too much for regular driving with a noticeably rougher ride, but is the ticket for hard flogging on your favorite ribbon of pavement.

Visual changes to the outside are understated, but functionally substantial with a different front bumper with larger air dams and front quarter gills to improve cooling, bigger side skirts, M-specific side mirrors, rear spoiler and rear apron. Making up for the added weight from the all-wheel-drive system is an aluminum hood and front quarter panels, while a carbon fiber-reinforced plastic roof appears on the M5 for the first time.

Cabin alterations consist of heavily bolstered sport seats that do a superb job of latching onto occupants during lateral maneuvers, M sports steering wheel and a red engine start button.

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Like the regular 5 Series, the intuitive iDrive 6 system handles infotainment duties with a 10.2-inch center touchscreen, available gesture controls, 16-speaker Bowers & Wilkins surround sound audio, navigation, 4G LTE Wi-Fi hotspot and a wireless charging pad. Apple CarPlay capabilities are also optional, but disappointedly BMW still doesn't support Android Auto.

The full menu of safety technology items found on other 5 Series models is also available. Those include a head-up display, radar cruise control, 360-degree camera, lane departure warning with steering intervention that isn't overly sensitive and frontal collision warning with automatic braking. The latter thankfully never gave off any false alarms or have a reason to activate during the street drive.

By this point, it may sound like the new M5 has gone soft with its friendly road manners and more substantial technology offerings. However, lapping Autódromo do Estoril behind BMW factory driver Bruno Spengler reveals otherwise. The turbo V8 is an animal with linear power delivery and a fat peak torque band from 1,800 to 5,700 rpm that hustles the 4,300-pound sedan out of turns with authority. The sole knock against the engine is the exhaust note that's nowhere near as thunderous and soul stirring as Mercedes-AMG V8s.

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High speed stability is solid down the long front straight where eclipsing 120 mph before jumping hard onto the brakes is typical. Optional carbon ceramic brakes with six-piston front and one-piston rear calipers slow matters before turn one with the car wiggling slightly during initial front weight transfer.

With the ZF transmission in its most aggressive setting, it does exceptional work ripping off well-timed gear changes in full automatic mode and responding to manual commands for both up- and downshifts. No major gearbox flaws surface during the six lap session around the 2.59-mile track.

Through the chicane and the long right hand sweeper onto the front straight, some understeer did show itself while attempting to keep pace with Spengler, who is the 2012 DTM champion. Considering the M5's weight, some push isn't surprising, but overall grip and composure through corners is exceptional.

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Understeer concerns disappear with the M xDrive system in the all-wheel-drive Sport setting to transfer more torque to the rear wheels and M Dynamic Mode enabling more slip angle before stability control steps in. The settings allow the back end to rotate around on throttle and get sideways easily requiring small counter steering corrections. Behavior is indeed similar to a rear driver being fun and involving, but with more corner grip.   

For the rear-wheel-drive purists still not sold on the all-wheel-drive M5, maybe M xDrive's two-wheel-drive mode will? Here, all power goes to the back wheels to appease enthusiasts with traditional driving dynamics and the ability to really hang the rear end out.

When the 2018 BMW M5 arrives in dealers next spring, it'll wear a $102,600 base price to slightly undercut the $104,400 Mercedes-AMG E63 S. Picking the right car for you between the two comes down to what traits you value the most. The AMG still holds the advantage on road with better ride quality, but the BMW makes great strides here, too. Out on a track, the M5 is the pick even with the automatic gearbox and all-wheel drive. Suspension and steering tuning give the BMW brisk reflexes and make for an entertaining time behind the wheel.

In reality, if you are deciding between the new M5 and E63 S, there really isn't a wrong answer.