For flight the Paralinx Tomahawk is really your best option. Lightest weight transmitter, and using our ARRAY (Tm) antenna set we have tested over 1 mile away in RF dense environments. An HD modulated RF system like the Tomahawk will always beat an encoder system in picture quality and latency - there are some benefits to encoding though like smaller data packet/radio link budget as Gaylen said. Paralinx has a few tricks up our sleeve relating to our video modem in Tomahawk that will be unveiled in time. I'm not 100% sure but if you are using a camera with hdmi like a blackmagic pocket cinema camera you will need an additional piece of hardware (added weight and power consumption) in order to work with the Vitec group/ IMT Microlite.