Choosing the major when they have equal length
Careful !
When you majors have the same number of cards, choose the one that does not have an Ace; This way, you'll preserve the Ace for the secondary suit and will have a stopper. In case of a singleton lead in that suit, you won't suffer the 'infernal ruff'. Singleton ♥ lead taken by East's Ace that plays it back for the ruff.