This is micromanagement 101. (Sorry this turned into a bit of a wall of text.)

If you find one-on-one meetings more productive than group meetings, then you are terrible at running group meetings. Full stop, I don't even need to know how good this guy is at running meetings.

Let's walk through some of the benefits the author lists first...

1) Participates can speak without boring others. This is an indicator of two possibilities. One, you have the wrong people at this meeting - that's your fault as a manager (and probably as the meeting leader/facilitator). Or two, you are running the wrong kind of meeting - again, that's your fault as a manager. Meetings should be purposeful, and every participant should have a purpose in being there. You as a manager (and hopefully your team) should consider this before every meeting (trust me, it's easier to do that than hold several times more meetings).

2) People can speak without being interrupted. If you're letting people interrupt each other, you're bad at leading meetings. If you're leading a meeting, you're there to serve the purpose of the meeting, not to be everyone's friend. Again, that's your fault as a manager.

3) They can offer negative opinions about their coworkers. Whoa. Now we're in really bad management territory. How are you going to go about conflict resolution once this person has confided in you? How are you going to be a neutral party? Not only that but giving you that negative opinion didn't solve anything.

4) They can offer positive opinions about their coworkers. Haha. What. "The too obvious incentive of their co-worker hearing their praise." Jesus. Where do you work? This isn't even bad management, this just sounds like a horribly unhealthy organization.

5) "If a person is running late on a project, the best way to find out the reason is to have a one-on-one meeting with them." I mean did you have to have a one-on-one meeting to find this out? If you have people that are unwilling to take responsibility for their (yes, their, not your) projects, then you need to check your hiring practices.

"They are free to incriminate themselves, in ways that I find useful." Jesus Christ. Again, where the hell do you work? In ways that you find useful? "For instance, they might put all the blame on someone else. After the meeting I will investigate their accusations and discover the truth." Or, if you had done this in a group setting, they wouldn't have had that option and you wouldn't have to had to go play Sherlock Holmes with your employees. But, I guess you have the free time? "If I’d called a group meeting, and that other person was in the room, it’s unlikely that anyone would have told me the truth." Or you could hire people that take responsibility for their actions.

6) "What if someone finishes a project much faster than I expected, or with much higher quality than I was expecting?" "It would be awkward to try to have these conversations while other people are in the room." I mean, maybe. They might have questions too, or be interested in the answers. Again, if you take the time to actually think about the purpose of the meeting you want to have you won't run into this problem. There is a time and a place for one-on-one meetings.

Now, let's look at some of the things he dislikes about group meetings now...

"As it was, during the typical meeting we had 15 people in the room, most of whom were bored." Whoa. What. 15 people!? That's twice as many people as you should probably ever have in a meeting.

"So who is right, and who is wrong?" Didn't see a whole lot of managing in that conversation. Do your meetings even have leads/facilitators? Who is holding the participates accountable for the purpose of the meeting?

"You’ll need to figure this out, but you don’t need to do so while 12 other people are in the room. If you are the manager who is overseeing this, it is up to you to get people back to work." Then do that, get the meeting back on track.

"A great manager doesn’t allow such debates to exist, because they don’t hold the kinds of meetings where this behavior is possible." WHOA. Nope. This is about as bad as management can get. Debates are healthy, conflict isn't bad. How else are you (and your organization) going to learn and grow?

There's a lot in there about "client" meetings, but not so much about internal meetings. Why is that? Sounds like the author is shifting the blame... I like to have managers that take responsibility for their actions...

So, what's the real conclusion of this article? Aside from there clearly being some "client" issues. One-on-one meetings are easy. Here's why:

1) They are easy to lead. Leading one is easier than leading five.

2) They avoid, more or less, all conflict. Even the productive kind. You can be everyone's friend.

3) They mean you (as a manager) don't have to think about who should attend.

4) Everything on your team has to go through you (I believe this is also called micromanagement).

They also are far less efficient and effective, if you know how to lead a group meeting.