The Alienware M18 R2 is a big laptop in every way, with an 18-inch screen, top-of-the-line processor, and graphics, all wrapped up in a package heavy enough to break your back if you pick it up wrong.

Traditionally, the usual screen sizes for gaming laptops have been 15 and 17 inches, but that has changed dramatically in the last few years. First, we saw ultraportable 14-inch machines from ...