The Suburban and Yukon XL are familiar vehicles on the road.   They share sheetmetal body panels but differ in details such as the grille, bumpers and lamps.   These are big boxes but quite smooth, rather like an ocean liner's long flat sides and tapered ends.   The Denali XL adds some of the upscale cues found on the Cadillac Escalade ESV, which shares the same basic structure.  

The running board/side steps are integrated and unobtrusive, extending no farther than necessary, with a black grippy coating; powered retractable steps are available on some models.   The tinted glass behind the C-pillar is expansive, and adds to both appearance and function.   The front end has a clean appearance, with beefy block-like headlamps over a front bumper fascia.   Doors close with a reassuring thud.  

Wheels change visual perceptions of the Yukon XL.   The standard aluminum wheel is a nice piece for look and function.   You can add 20-inch wheels, some polished aluminum and others chrome-clad wheels that merely add a chrome-plated plastic cover to an existing wheel and could fall off or pack snow and muck depending on how you abuse your truck.   Dealers offer a host of dress-up items, including wheels up to 22-inches.   The standard 17-inch wheels offer the best ride quality due to tires with tall sidewalls.   Ride quality gets harsher as wheel diameters go up.  

The rear window opens separately, which is convenient for loading lighter bags and cargo.   The larger liftgate is aluminum and balanced, upgradeable to power for those accustomed to a push-button world.   Roof racks can carry unwieldly items that aren't too heavy, but be sure to load with the hatch open or after the cargo area is filled so the roof load doesn't interfere with the open hatch.