Are you looking for anything specific? I can't personally vouch for Xbox One as for not owning one but I own a Switch and so this may be a bit biased. Maybe get an Xbox One if you're more interested in triple-A, want a dedicated console (not saying the Switch is any worse, no!) or prefer entertainment options (that's one thing the Switch doesn't have yet, no Netflix yet or anything like that) or something.
Anyhow, despite the doubt it's kind of received, I'd say you wouldn't really go wrong with the purchase of a Nintendo Switch. It's doing pretty strongly despite the expected competition from the Xbox and PS4 and you're far more likely to be able to snag an unit now than it was like weeks after launch. You probably know that, given how horrible the stock issues were for months.
I would suggest buying an SD card additionally too along with a glass screen protector, as the console only has 32 GB of HD space. Not sure if you own an Elgato device but also that too, if you want to stream Switch games.
The portability is a great feature (so is the fact it has a built-in UPS and the switch from portable to docked is seamless) and you and your wife will likely grow to love that feature and the ability to undock and take it...anywhere! It's very portable (even if that's the point) and it's far more comfortable than the like of something like a laptop.
Zelda and Mario are definitely it's killer apps and unless you don't like one of those, both are really good to pickup as your first games of choice besides an indie game or two. You won't be disappointed with Super Mario Odyssey, I almost guarantee. The system has a pretty massive indie library going for it that is pretty strong at the moment and the console is being helped by the presence of bigger games like Rocket League, Wolfenstein, Skyrim, LA Noire, Payday 2, Steep, and Doom.
To give you an idea of just how massive it's current and upcoming indie support is, here's a somewhat small list, even if it's the more well known titles:
1001 Spikes, Axiom Verge, Isaac Afterbirth, Cave Story, NecroDancer, Darkest Dungeon, The Escapists 2, Golf Story, Hollow Knight, Morphies Law, Mighty Gunvolt Burst, Stardew Valley, My Time at Portia, Octodad, Owlboy, Shovel Knight, Slime-san, Retro City Rampage DX, Oxenfree, Runner3, Sine Mora, Wargroove, The Sexy Brutale, Snake Pass, Enter the Gungeon, Farming Simulator, Fast RMX, GoNNER, Little Inferno, Graceful Explosion Machine, SteamWorld Dig 2, Super Meat Boy, TumbleSeed, This Is The Police, Ultimate Chicken Horse, VVVVVV, World of Goo, Portal Knights, Rive, Runbow.
