As always, depends on the set and situation, but usually Draco Meteor is better.
Miraidon usually runs Draco Meteor on Choiced sets, in order to do as much damage as possible, Specs specifically 2HKOing the best checks to Miraidon, namely Clodsire and Ting-Lu, while Pulse can only hope to 3HKO.
- 252 SpA Choice Specs Hadron Engine Miraidon Draco Meteor over 2 turns vs. 252 HP / 252+ SpD Clodsire: 470-556 (101.2 - 119.8%) -- guaranteed KO in 2 turns after Leftovers recovery
- 252 SpA Choice Specs Hadron Engine Tera Dragon Miraidon Draco Meteor over 2 turns vs. 252 HP / 252+ SpD Vessel of Ruin Ting-Lu: 544-644 (105.8 - 125.2%) -- guaranteed KO in 2 turns after Leftovers recovery
- 252 SpA Choice Specs Hadron Engine Miraidon Dragon Pulse vs. 252 HP / 252+ SpD Clodsire: 205-243 (44.1 - 52.3%) -- guaranteed 3HKO after Leftovers recovery
- 252 SpA Choice Specs Hadron Engine Tera Dragon Miraidon Dragon Pulse vs. 252 HP / 252+ SpD Vessel of Ruin Ting-Lu: 238-282 (46.3 - 54.8%) -- 9.8% chance to 2HKO after Leftovers recovery
All in all, Draco Meteor is used on pretty much every viable Miraidon set except most Calm Mind + Life Orb sets and sometimes Double Dance sets (but those usually only attack with Parabolic Charge and Tera Fairy Dazzling Gleam). Dragon Pulse tends to miss out on these notable threats, which is why Draco is still much more widely used, even with that SpA drop. Home connectivity hasn't changed much with Miraidon, other than the prevalence of HDB sets over Choiced, which also sometimes run Pulse, but Draco is just better.
Hope I helped!
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