Don't buy the LRs (Long Range versions for those not familiar with the Ubnt naming) unless plan on a low density+large+wide open space (e.g. an auditorium where only staff have wifi access).
The trick to GREAT wifi coverage is to turn the power down on each access point as low as you can, and have as many APs as you can. Wifi is a two way street, e.g. even if your AP can blast a signal through 5x 10ft thick walls, it won't matter in the slightest, since your phone or laptop etc won't be able to do the same.
In fact - that's a lie :) It will matter, it will hurt the end user experience. The phone etc will see a "strong" signal, select it, but outbound packet loss will be terrible.
The trick to GREAT wifi coverage is to turn the power down on each access point as low as you can, and have as many APs as you can. Wifi is a two way street, e.g. even if your AP can blast a signal through 5x 10ft thick walls, it won't matter in the slightest, since your phone or laptop etc won't be able to do the same.
In fact - that's a lie :) It will matter, it will hurt the end user experience. The phone etc will see a "strong" signal, select it, but outbound packet loss will be terrible.