1. GATT was ad hoc and provision but WTO and its agreements are permanent.
2. GATT had contracting parties but WTO has members.
3. GATT system allowed existing domestic legislation to continue even if it violated a GATT agreement. But WTO does not permit this.
4. GATT has less powerful dispute settlement system which is also slow and less efficient, its ruling could be easily blocked. But WTO is more powerful then GATT dispute settlement mechanism is faster and more efficient and very difficult to block the rulings.