There has been confusion on this subject before, so let me elaborate. 

Many routers these days support dual-band frequencies (2.4GHz and 5GHz) to minimise interference when on a wireless network.

2.4GHz has the advantage of having longer range, so it can penetrate walls more easily and reach almost all areas of the house. However, it isn't nearly as fast as 5GHz is - if you have high-speed fiber interent you'll have trouble getting full-speeds out of it. Also, it's prone to interference from other routers and microwaves/cordless phones, causing packet loss and dropped connections in places such as urban areas. If you see constant communication errors in Mario Kart games, often it's beacuse of this. It's generally not recommended for online gaming.

5GHz has shorter range, but it's much more reliable, due to how uncluttered the frequency band is. It also supports much more bandwidth (fibre optic connections benefit). The Wii U GamePad uses this freqnecy to connect to the console, and as a result, it has lower control latency than most TV's! Online gaming benefits too, with little to no packet loss.  However, due to the shorter range, people living in homes with thick walls won't be able to use this band unless they are right next to the router in the same room.

Now, as wired internet obviously isn't an option for handhelds, I feel like Nintendo should cater to best of both worlds with Dual-Band a/b/g/n/ac Wi-Fi for the NX. That way, both crowds can be satisfied. 

I still think there will be two models. The basic one, the handheld that can also connect to the TV, and a Vita TV-like console. Without screen and batteries, they could focus more on giving a more console-like experience, specially because I don't see the handheld version having a physical port for internet connection, and that is going to cause a lot of troubles. Plus, you know, price and all...

Informative, well explained thread. Thanks!

You're welcome! 

I'm just really really hoping that Nintendo won't cheap out on Wi-Fi just because "they're Nintendo". For me, 5GHz has been a godsend for fixing my Wi-Fi woes, and it's helped my family too! 

Doesn't matter what kind of technology NX uses if the mainstream wireless router can't facilitate it. It will also not solve band clutter which will worsen in the future. The only chance for a proper connection is to place your access points better and to use the least use band in your neighborhood.

I'll never use 5ghz, like you mention, the range is appalling.

2.4ghz is more than enough, especially for a Nintendo system.

Thats what the dock's for. HDMI, USB, Ethernet etc

Oh, right, the dock. Forgot about it for a moment. Kinda makes me wonder all the stress the dock is going to need to deal with, but I suppose that tech is tested enough at this point.

It also works the other way round. My router supports 802.11ac 5GHz. Nearly all my devices connect to that no problem. Only the dated iPhone 4 needs it. Why should the NX be any different? 

For YOU, it's more than enough. But for others like me, it's borderline unusable due to high interference. This is why I hope the NX supports dual-band, to satisfy both crowds. 

The Wii U gamepad uses it so Nintendo knows. There shouldn't be any reason why NX wouldn't have it. The problem is its connection issues.