With the AP One Rugged, you have three RP-SMA connections, as each of these is able to do both 2.4Ghz & 5Ghz, then you will need to ensure your antennas are suitable frequency matched, remember that the units will need to be well protected also from the environement.
We have been rolling out the AP Pro Duo units in some extreme outdoor environments where we have been powering some of the units with solar power. You may find these a better option and worth the extra expense, these have N-Type connection and are more suitable robust for outdoor environments.
Most important is to correctly match your antenna systems (and cables if used) to the connection type, do not skimp on quality and seriously consider extra lightening protection.
In Australia we recommend antennas made by both RFI Wireless & Telco Antennas. Telco Antennas supply both internationally and you may have a local re-seller nearby if the shipping costs are of a concern.
A note on Wi-Fi device roaming: this is actually the responsibility of your portable WI-Fi device not the WAP regardless of the manufacture, Peplink along with most enterprise bands of WAPs have techniques in place to help encourage Wi-Fi devices (such as refusing to connect devices based on signal strength) though at the end of the day your Wi-Fi device has to make the choice as to which WAP it connects to. Do not let the marketing hype out there confuse you, wireless WAP controller or not, the Wi-Fi portable device is responsible for choosing and switching WAPs not the WAP.
Happy to Help,