You can use the AVL50 with Fatshark goggles if you replace the receiver in the Fatsharks with one that supports the Boscam frequencies. You can do this with the Dominators.
I use the Attitudes and for my S800 where I have the AVL58 and I use a separate receiver which has a cable going to the Fatsharks. This enables me to have both a monitor and the goggles at the same time.
As for reliability of the different transmitters, they are all much the same. Higher mW = longer range but good antennas helps more than power.