Not sure if it's been mentioned, but the 'channels' on 2.4GHz are a bit of joke since the sidebands of just one extend over about half the entire band. Thus it's a bit like AM radio at night.
The 2.4 GHz channels were defined before WiFi existed. The channels have a width of just 5 MHz, while a WiFi transmission on 2.4 GHz has a bandwidth of 20 MHz. Some stupid manuafcturers even suggest using 40 MHz channels on 2.4 GHz, which is even worse. In that case the whole band can only carry two simultaneous transmissions.
These graphics on Wikipedia display it pretty well.
Most of the WiFi problems come from poor configurations. And of course the 2.4 GHz spectrum is saturated just because of the number of users.
5 GHz is better for several reasons:
- Its suffers more attenuation due to walls. I would say "benefits" because your neighbor's 5 GHz network will rarely be a problem. But
of course you may need several access points at home depending on the number of rooms, its structure and even the kind of walls you
have.
- There is much more bandwidth available, which leads to higher speeds.
- There are plenty of crappy devices on 2.4 GHz like audio/video transmitters, etc. Some microwave motion detectors operate on 2.4 GHz. Bluetooth operates on 2.4 GHz. Microwave ovens radiate on 2.4 GHz. The 5 GHz band is cleaner. Anyway, at least your neighbor crappy
devices will be less of a problem on 5 GHz thanks to attenuation.
And there are some misconceptions around power. More power on the access point makes it visible at a larger distance but it doesn't
mean you will achieve a larger range. Using a 1 W ERP accesss point doesn't make your phone, tablet or computer radiate 1 W. Actually,
in places covered by several access points it's usually a good idea to decrease AP power so that devices associato to the nearest
AP.
Apart from interference, the worst WiFi performance killer is devices associated with a poor signal level. Those devices need to transmit
at a lower speed (otherwise they wouldn't work) and that drags down the rest of the associated clients because it takes up more
radio time. If you have several devices at home check the list of associated clients.
Antennas: even built in antennas can be very different. Enterprise access points designed to be attached to the ceiling are intended to
be unobtrusive, so you will rarely see connectors for external anntennas. Some el cheapo residential APs have external antennas
because they are very cheap and visible atennas are probably perceived as "more powerful" by most users. But some enterprise
APs have quite sophisticated internal atennas.
The main benefit of a proper antenna is not just radiated power, but
rejecting interference. An example: An AP with a good antenna radiation diagram attached to the ceiling will be much less sensitive to transmissions from the next floor, which means it will be
more immune to interference from your neighbor and, in case you own both floors, it will make it less likely for a device on a floor
to associate to an AP on a different floor, which is good.