The tiger trout grow slower initially according to an email from a state hatchery superintenent in Massachusetts. However they catch up and surpass the other species due to a lack of stress and wasted calories in gonadal activity.
The draw to anglers is their aggressiveness and as you guessed uniqueness. Personally think a male brook trout in full spawning colors rivals a tiger trout but I know anglers and taxidermists that go googoo eyed over them.
Allegedly they are also hardier than even a brown trout according to my hatchery egg source and a prof that wrote an article a few years ago. Supposed to hang in there better when oxygen and temps are marginal. Seems counterintuitive as they are partly brook trout but...
Also in a couple of the western states they claim they can be used to control an invasive species known as tui chub and golden shiners.