2.4 GHz? 5 GHz? Bigger numbers are better right?

With the release of the 802.11ac wifi protocol earlier this year, 5 GHz wifi hardware has seen an increase in popularity.
Because it is newer and faster and better right?

Despite the larger number, 5 GHz wifi is just as old as 2.4 GHz, but the hardware was more expensive to manufacture which hindered early adoption.
As far as speed goes, the frequency value associated with wireless routers isn’t processor speed like with computers, it is the frequency of the radio waves it broadcasts. Higher frequency waves can transmit more information, but at the cost of reduced range. Lower frequency waves are also better at penetrating walls, an important consideration for your home wifi network.
The factor that is really beginning to emerge however is that 2.4 GHz is too popular. Every house in your neighborhood has a 2.4 GHz network. Your Bluetooth keyboard, mouse, headset, and Food Probe all broadcast in the 2.4 GHz range. Your FreshSense system claims to be Zigbee in the instructions, but that is yet another system that broadcasts at 2.4 GHz. I’m told some people still have home phones, 2.4 GHz was a popular choice for cordless phones too. Even your microwave creates 2.4 GHz waves (though if too many are escaping you should probably get a new one). All of this competition over a limited frequency range can lead to connection difficulties, so the primary appeal of 5 GHz wifi is that fewer people are using it.

Gee that is all so complicated. I came here for consumer advice, do you have a simple rule of thumb?

Yes dear reader.
If you are reading this article in a cave under your mansion and are unsure where your butler even plugs in the router, range considerations suggest you should use 2.4 GHz.
If your guests always have to ask which network is yours because there are 38 different networks in your building, and your couch is in the same room as the router, switching to 5 GHz wifi may improve your performance.