You will find almost everything commonly used in the cruising community is based on either the Ubiquiti Bullet or the Alfa (note spelling). I have both. I find the Bullet systems (IslandTimePC, WifiForBoats, Bad Boy, etc.) to have better effective range than the Alfa (Alfa, Wirie). The specs can be hard to pin down but it does seem the receiver performance of the Bullet is the determining factor. With a Mac (or more?) aboard you may also find the Ethernet-based interface appealing - there are many less issues with drivers and such than a USB solution.