Best Wi-Fi vs long-range Wi-Fi

There are currently two different WiFi bands: 2.4 and 5 GHz. In the 2.4GHz band there are several different available protocols: 802.11b/g/n. Virtually no one used .11b anymore, as it's too slow. .11g and .11n are better, but the 2.4 GHz band is crowded with so many other devices and there's a limited number (3) of channels that don't interfere with each other. On the 5 GHz band, you have much higher speeds and less interference. It also has a number of protocols: .11n (yes, the same protocol used on 2.4GHz), .11ac and .11ax. No current Roku support the .11ax protocol, but .11ac is more than fast enough for any streaming source. I get about 220 Mbps on 5GHz when I am close to the access point. Nothing streaming from the Internet really uses more than about 25 Mbps. 

But there are tradeoffs between the two bands. While the 2.4GHz band is more crowded, it has longer range than 5GHz. Signals passing through floors and walls drop off quicker on 5GHz. That said, I can still use my 5 GHz connection anywhere in my home with a decent signal, and my home has three floors and almost 3800 sq ft. 

Every current Roku player (and I believe all TVs) except for the Express and Premiere are dual band, so they support both radio bands. I recommend a dual band device if at all possible, simply because 5 GHz is less crowded and has the potential for greater speed. 

You may hear the term WiFi 6. It is now the official name for 802.11ax, but in its basic form still uses 5 GHz. They are now developing WiFi 6e, which will use a new 6 GHz radio band. At this time, no Roku device supports any form of WiFi 6.

I'm assuming you're referring to the terms that Roku uses on its compare features page.  ie: Sticks have "long range Wi-Fi" whereas Ultras have "Our best Wi-Fi".  I would assume (hope!) that "Our best" is really the best (including longest range), though I don't know if anyone has tested that.  I would assume something like this isn't that easy to reliably/repeatably test in real world conditions.