The power difference between Choice Specs Latios's Draco Meteor and +1 Life Orb Latios's Dragon Pulse is significant. This is on top of the turn that it has to spend using Calm Mind. The calcs I'm getting are:
+1 252 SpA Life Orb Latios Hidden Power Fire vs. 252 HP / 252+ SpD (custom): 179-213 (45.43 - 54.06%) -- 44.53% chance to 2HKO
+1 252 SpA Life Orb Latios Dragon Pulse vs. 252 HP / 252+ SpD (custom): 173-204 (43.9 - 51.77%) -- 9.77% chance to 2HKO
Yes, there is something to say about Dragon Pulse still having a chance to 2HKO without criticals, so that may be a reason to bump up the special bulk a little bit more. However, in the end, it seems to me that it is not quite as worrying as Choice Specs Latios would be. Plus, with Hidden Power Fire, Latios is sacrificing either Surf or Recover/Roost and that comes with its own problems.