The EU mutual defense clause is even stronger than Article V of the NATO treaty:
Nato Treaty:
“The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognized by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area."
Translation: Every NATO member can bloody well decide for themselves ("as it deems necessary") how to help another member state.
Article 42/7 of the EU treaty:
"If a Member State is the victim of armed aggression on its territory, the other Member States shall have towards it an obligation of aid and assistance by all the means in their power, in accordance with Article 51 of the United Nations Charter."
Translation: You got to give it everything you got ("all means in their power"). If Ukraine had been an EU member, the treaty would have required other EU member states to send ground troops.
Of course, international treaties can not be enforced, if the treaty parties don't want to comply. So in reality, both treaties rely on mutual accepted norms of behavior more than on the letter of the law. Which is why Trump's behavior has been so damaging to the NATO alliance, without any actual test of it. And while the EU's treaty is worded stronger than NATO's, it has never been formally used or tested.
Nato Treaty:
“The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognized by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area."
Translation: Every NATO member can bloody well decide for themselves ("as it deems necessary") how to help another member state.
Article 42/7 of the EU treaty:
"If a Member State is the victim of armed aggression on its territory, the other Member States shall have towards it an obligation of aid and assistance by all the means in their power, in accordance with Article 51 of the United Nations Charter."
Translation: You got to give it everything you got ("all means in their power"). If Ukraine had been an EU member, the treaty would have required other EU member states to send ground troops.
Of course, international treaties can not be enforced, if the treaty parties don't want to comply. So in reality, both treaties rely on mutual accepted norms of behavior more than on the letter of the law. Which is why Trump's behavior has been so damaging to the NATO alliance, without any actual test of it. And while the EU's treaty is worded stronger than NATO's, it has never been formally used or tested.