Being more efficient means less time allocated to meetings.
Estimates vary but there is consensus that managers spend some 25% to 40% of their time in meetings. It is not just the meeting time but the travel time that adds to the time commitmet.
Being more economic means that the cost of meetings is less.
Time is money, travel and accommodation also costs as does venue hire, etc.
Being more effective means that the end result is better.
It may be better as it is cheaper and faster. Maybe it is better as the presentation of facts was available sooner giving more time to study the implications.