IME, hardiness parallels size... but for different reasons. Juveniles are the least hardy but the quickest to adapt to aquarium life and the least risky to eat corals (although I wouldn't trust them). The adults are the hardiest but have more difficulties adapting to aquarium life and tend to stress out more easily and are the first to eat corals. So I say shoot in the middle. An adolescent, about 3-5 inches will probably give you most upside with the least amount of downside.
As with many fish, those with the most personality tend to be the most aggression. These are no exception, but there's nothing wrong with them being the boss as long as they can coexist. Pick good tankmates, feed them well, good filtration and strategically aquascape your aquarium and all should be good... until it outgrows the 140... but then you get to upgrade tank size, or start over with another or start over with another large angel species. All choices are winners. Good luck.