Our company installs Wi-Fi systems in marinas
and yacht clubs. A typical installation
will see 6-8+ APs, installed high (40-50' up) and pointed down onto the harbour area from above. This is to give everyone a good opportunity to get as much of an unobstructed line of sight to one or more APs. When we tested with different antenna gains, we found anything over 8.5dBi didn't connect with the closest APs. This was because their radiation pttern was too flat and the APs they connected with were on the other side of the harbour. They were going through the metal forest and would experience dropouts.
In our experience, most people do not want to hoist antennas up a halyard
or tinker with parabolics, etc. (I truly appreciate those who do - makes my job easier.) Users don't want to carry different antennas to accommodate for different locations. They don't want to know about attenuation, SNR, noise floor or dbs. They just want to get on the net. Truth is that the majority of the time, people are going to be less than 1 mile from the AP. A 6dBi antenna has an unobstructed range in excess of 3 miles (we've tested to almost 5nm) when coupled with a 1000mW radio and connecting to a suitably capable AP. That's why we only offer a 6dBi. I just returned from the Grenadines where we logged in everywhere using a 6dBi omni - no muss, no fuss... just turn on and go. Anything over 8.5dBi may be OK when you'll be staying anchored for a long time and need the extra bit of range.
Regarding Ubiquiti "Obey Regulatory Power": That checkbox is only to limit the power based on the restrictions of the country selected. Changing antenna gain will have no effect on this value.
BTW: How do you recognize a 'cheaper' antenna?
Sorry for the long post. This is a great forum!