Despite the incredible proliferation of crossovers throughout BMW's lineup, the brand has been slow to add M variants of the high-riding machines. Until this year, the only BMW crossovers to get the M treatment have been the X5 and its low-roof twin, the X6 . But now the company has added not just M, but M Competition versions of its X3 and X4 compact crossovers The company has gone to significant lengths to upgrade the vehicles for M duty, which we focused on during this drive, since we've covered the crossovers' practicality and comfort in our previous reviews of the basic models . Though we had limited time in the X3 M , most of our time, both on the road and track, was spent in a 2020 X4 M Competition. It's clear BMW M's extensive lengths to improve the model have paid off in a quick and sporty crossover, but it's one that you should think twice about before using on a daily basis.From the outside, neither M vehicle looks much different from its normal kin, save for more aggressive grilles and spoilers. But underneath, there isn't a whole lot to connect them. The engine, for example, is almost completely new — 90 percent new to be exact, when compared to the M40i's engine — and it's being used for the first time in the M crossovers. It's a 3.0-liter twin-turbo inline-six with a closed-deck block; forged crankshaft, pistons and connecting rods; an air-to-water intercooler; and several radiators for engine, transmission and intercooler cooling. It even weighs 20 pounds less than the 425-horsepower 3.0-liter straight-six in the M4 . All the while, it makes 473 horsepower and 442 pound-feet of torque in the regular M, and power jumps to 503 in the M Competition model thanks to a retuned ECU and unique exhaust.That engine is coupled to an eight-speed automatic transmission and an all-wheel-drive system that's the same as the one in the M5 , just with different casings and axles. This also means that by default, all power goes to the rear wheels unless slip is detected. The amount of slip and intervention varies depending on the drive mode and traction control settings. The more aggressive the settings, the less front-drive assistance you get.The M models get uniquely tuned adjustable shocks, bushings, and even a new steering rack. More chassis bracing has been added, too. The brakes feature 15.6-inch rotors and four-piston calipers up front, and 14.6-inch rotors and one-piston calipers in the back. And the only difference between the regular M and the M Competition, besides the aforementioned power increase, is that the Competition gets stiffer sway bars.Of these changes, the X4 M's engine is the one that leaves the biggest and best impression. The power delivery is so smooth and the throttle response so crisp, it feels like a naturally aspirated engine. Every wiggle of your toes prompts an immediate reaction; there's never any waiting or unexpected surges of acceleration from the turbos. The real benefits of this show up on track where you can floor it with confidence and be incredibly precise with throttle applications through corners. On public roads, the engine is just as smooth in refined driving as it is with raw power delivery. Be sure you have the exhaust set to quiet: In loud mode, it can drone, especially at highway speed.The eight-speed auto is a great supporting actor for the engine lead. Around town in its least aggressive setting, it's seamless and unobtrusive. Crank it up to full aggression and shift it manually, and the shifts become more abrupt, and quicker. You can even coax out some pops and bangs from the exhaust with the aggro shifts.Whereas the engine and transmission are happy anywhere, the suspension and chassis are clearly happier on the track than on the road. Even in the Comfort setting, you'll be kicked around by every crack and bump, and the sportier settings reveal to your backside ever smaller ripples and grains in the pavement. At the same time, the steering is silent about road conditions, something M cars have been bad about the past few years . Choosing sportier settings only adds heft rather than communication. The brakes are overkill for the street. Press too hard on the soft pedal and you're in for a sudden stop, at least until you're used to the brakes' aggressive bite.Further evidence that the X4 M Competition isn't so happy on the street comes in the form of constant road and tire noise, plus some loud wind noise from the A-pillars at highway speed. The M-specific seats also have low, firm bolsters that are on the tight side for larger bodies, but they also don't provide much holding power on the track.Leave the streets, and the rock-hard chassis comes into its own. It feels composed and impressively neutral, only ever upset by carrying too much speed into a corner or giving the throttle a hard stab. The chassis gives you loads of warning when it starts to understeer or oversteer, so it's easy to keep the car under control. The steering remains indifferent, but at least it's accurate and builds weight naturally. The brakes always delivered strong, confidence-inspiring stopping power, though the pedal still felt uncomfortably soft.What BMW has created may not be a great daily driver, but the X4 M Competition and its more practical X3 twin are still impressive. It goes incredibly fast, and it doesn't fall apart on track. In fact it relishes a closed course. And isn't that what an M car is all about?