Both are mobile consoles, letting you game on the go.
The Nintendo Switch, however, can be docked for TV mode. This will usually give you a better visual presentation (not just in resolution, but also extra graphical detail) compared to playing on the device's screen.
The Switch is 9-percent taller, 50-percent wider and 35-percent thinner than this 2015 3DS XL.
For thickness, though, keep in mind that it measures the 3DS while closed: It will be thinner than that, in your hand, while playing.
The Switch, despite having much more powerful internals, is 13-percent lighter.
Nintendo has gotten better at making plastic look somewhat premium (as evidenced in both of these sharp-looking gadgets), but don't expect to see any aluminum or other metals.
The Switch has a 56-percent bigger screen, compared to the 3DS XL's main (top) display.
Pixel density isn't even close, as the 3DS XL wasn't pushing any barriers on this front even when the first version launched nearly five years ago. The Switch's screen is 147-percent sharper.
Stereoscopic ("3D") display
Nintendo was trying to capitalize on the (largely ill-fated) 3D fad when it launched the first 3DS. The company stuck with the glasses-free tech during the duration of its latest portable's life cycle (apart from the cheaper 2DS), but Nintendo is dropping that focus with the Switch.
This "New" 3DS XL has face tracking that gives you a more stable 3D experience compared to the original models of the 3DS and 3DS XL. (On the older versions, you had to face the screen straight-on, but with this 2015 refresh you can angle the screen and maintain the illusion.)
Both devices have a touchscreen, though in the 3DS it's only the bottom display.
The 3DS also has a stylus that slides into the unit.
Both systems support small cartridges, as well as digital purchases.
The Switch will have greater potential moving forward (by supporting much more advanced and graphically-intensive games), but the 3DS platform currently has an enormous lead in content. At launch, the Switch only has one notable flagship game in The Legend of Zelda: Breath of the Wild.
Just a few of the many first-party 3DS games include: Super Mario 3D Land, New Super Mario Bros. 2, four major Zelda games (Majora's Mask 3D, Ocarina of Time 3D, A Link Between Worlds and Tri Force Heroes), Mario Kart 7 and two Yoshi games (Poochy and Yoshi's Wooly World and Yoshi's New Island).
For this reason alone, you may want to second-guess that instinct to snatch up a Switch as soon as possible.
The 2015 3DS XL, in addition to playing all 3DS-platform games, also supports old Nintendo DS (and DSi) titles.
Unfortunately you can't physically play 3DS (or any other older) games on the Switch.
The Switch will, however, eventually support Virtual Console, which lets you buy digital versions of Nintendo games from older consoles. But it isn't available at launch.
You can tilt and move either system for control in games that support this.
You can also pull the Switch's Joy-Con controllers off the sides of the device, and they have motion control of their own (similar to Wiimotes). This is also how you play the Switch in table mode or when docked to a TV, as the two controllers can either be used separately or slid onto a more traditional gamepad setup.
Estimates are similar, but if you're playing a graphically-intensive game like Breath of the Wild on Switch, expect to get less than six hours of battery life.
Fortunately you can charge either system on the go, with the proper cable and a portable battery pack.
The 3DS only has a measly 1 GB of internal storage, compared to 32 GB for the Switch.
You can, however, pop a microSD into either system to expand that. (The 3DS includes a 4 GB one preinstalled in the system.)
Note that you'll need to format a microSD to FAT32 to use cards greater than 32 GB in the 3DS XL.
The 3DS also has both a front-facing camera and a pair of stereoscopic rear-facing cameras.
The Switch has an infrared camera on the right Joy-Con controller (used to enhance hand recognition), but none on the main unit.
If a family kiddo is going to be playing either system, you'll be able to tweak what they can and can't do on the machine.
This "New"-branded model of the 3DS XL launched in the US over two years ago, but the 3DS line has been around since 2011.
At only US$100 extra, the much more powerful Switch is going to make a compelling alternative to the 3DS XL. Just keep in mind that a new gaming platform's first year or so can often make for a painful early-adopter experience (as evidenced by the single notable title you can play on it right now). Despite its old-fashioned hardware, the 3DS can provide many more hours of fun today.
So when do you want to buy the Switch? Of course there's no universal answer, but by this holiday season, it will have a flagship Mario game in Super Mario Odyssey, along with the current Zelda title, a port of Skyrim, Splatoon 2, Mario Kart 8 and NBA 2K18, among others. That sounds like a much more enticing offer than today's lineup.