The difference is in the frequency range that they pass.
Flex flow 2.3-2.4 GHz, WiMAX'marketing — 2.5-2.7 GHz.
There are antennas that allow a wide range, including WiFi'-ing frequency, and WiMAX'marketing, but they usually not ice are working.
The experience of using some kind of WiFi antenna was working with the WiMAX modem, but only in about one case out of three. The fact is that while connected to the modem basovka emit a range of frequencies. If this range in the early WiMAX'ovskogo — this antenna worked, if at least in the middle — all, it was only worse from it.