An important metric to consider when buying beacons is the transmission range of the hardware. There are a lot of things that affect this, such as whether the target device is in a straight line, or if there are any obstacles in the way, like glass, walls etc.
The maximum range for different hardware types are as follows -
Indoor beacon - ~80 metres (Transmission power @ +4dBm)
Outdoor beacon - ~80 metres (Transmission power @ +4dBm)
Pocket beacon - ~50 metres (Transmission power @ +4dBm)
Keychain beacon - ~25 metres (Transmission power @ +4dBm)
Long-range beacon - ~300 metres (Transmission power @ +4dBm)
Here is a table that specifies the transmission power to be set to achieve the required transmission range:
To obtain the most out of your beacons make sure that
There are no obstructions near the beacons to reduce signal strength (like walls, plants, etc). Usually the center of the room is a good place.
Place the beacons at a higher point to cover maximum distance.
Although higher transmission power will increase effective range, it also decreases battery life, make sure to play around with the hardware settings to get the best battery-life/range combo.
To know more about the hardware specification of different beacons, please refer to this comparison sheet.