The argument will go on forever... coaches want swimmers to SWIM off the walls, while swimmers want to grab some well deserved AIR! All agree, however, that the fastest you'll be going as a swimmer in a race, is off the walls.
The first breath off the wall after a freestyle flip turn can make, or break, your race. This drill describes three options for taking that first breath, and then you'll have to decide which is right for you.
Every swimmer must discover the balance between maintaining velocity... and getting air. This is especially true on each pushoff. Glide too long and you lose velocity (but you get that little bit of extra "down" time). Go to air too soon and you also lose velocity. You have to develop a feel for the timing that gives you the best of both -- enough velocity to travel fast and enough air to manage your overall energy throughout a race.
If you've been using option #1, then option #2 is MUCH better.
Option #3 is by far the best. It lets you maintaining the most momentum. Sure, you'll hurt for a few tenths longer, but that pain will subside when you see how much you've just gained on the swimmer in the next lane.