Efficiency is paramount in parkour, but I believe it's also a great idea to have more "inefficient" techniques at your disposal. One never knows when you might have to bail, and turn it into another vault as your landing, or when situations change and suddenly your intended vault will no longer work (as Moonrunner posted). Besides. Why would you say "That is slightly less efficient than <this>, so I'm not even going to bother learning it." Learn all you can! That's my motto.
Just something I was thinking about the other day.
PS. Speaking of learning all you can, Mac keyboards are so confusing.