How many ways are there to make a BLT sandwich? How many different varieties of lettuce do you have to offer? If you asked BMW product planning executives, I suspect they’d check the commissary menu at Mercedes-Benz and say, “One more than they do.”

Obsessive one-upmanship is the best explanation for a proliferating BMW model line that now includes the three-star 2014 640i xDrive Gran coupe. Unpacking that mouthful of a name, the car is one of BMW’s midsize 5/6-series models: powered by a 3.0-liter straight-six turbo; all-wheel-drive; four doors; holds four passengers and looks a bit sportier than the 540i sedan, but less so than the 640i coupe.

Would you like iceberg or romaine on that? Arugula? Radicchio? How about kale? I hear Mercedes has kale.

When a car company slices its model line into servings that thin, it’s tough to create compelling reasons to choose one car over another.

That’s the first challenge facing the 640i xDrive Gran Coupe. It shares most of its features with BMW’s 5-series sport sedan, 5 Gran Turismo hatchback and 6-series coupe, so some sibling rivalry on the showroom floor is inevitable.

The second and greater challenge is that the 640i Gran Coupe competes with a lot of excellent cars from other luxury brands. The pack includes low-slung design exercises like the Audi A7 and Mercedes-Benz CLS and more conventionally proportioned sport sedans such as the Cadillac CTS, Infiniti Q70, Jaguar XF and Lexus GS 350.

Prices for the 6-series Gran Coupe start at $77,600 for a 315-horsepower, 3.0-liter, rear-wheel-drive 640i. An eight-speed automatic transmission is standard on all models. Adding all-wheel-drive raises the price to $80,600. The 650i Gran Coupe with a twin-turbo 445-horsepower, 4.4-liter V-8 goes for $88,900 for rear-drive and $91,900 with AWD.

The 640i xDrive Gran coupe I tested stickered at $88,750. Its features included front and rear parking sensors, navigation, Bluetooth phone and audio, a sun roof and heated front and rear seats.

That’s at the expensive end of the spectrum versus the competition, but it lacked some features found on less expensive cars, like blind-spot alert and cooled seats. It’s a striking vehicle, with a long hood and wide stance. Its low roofline takes a toll on rear passenger space and creates narrow rear door openings for awkward entry. The trunk has plenty of room and a reasonably wide opening.

The front seat is accommodating, with useful cupholders, storage space in the center console and map pockets. The interior of my car featured two-tone leather, black wood and understated bright work.

The gauges are big and simple. BMW’s iDrive rotary controller continues to improve, though I still think a good touch screen is more intuitive. The gaps between the trim on the inside of the doors and the A-pillars were wider than they should be in a luxury car.

For decades, BMW’s engines whipped the competition, but other leading luxury brands have caught up. The 3.0L is beginning to feel a bit timeworn. Its horsepower is mid-pack, though lavish torque at low engine speed remains a strength. The eight-speed transmission is quick and smooth and helps deliver class-leading fuel economy.

So, would you like endive on that BLT? It’ll cost you.