Why did Sirius suggest the Three Broomsticks as a better meeting location for Dumbledore's Army?

Question

Is there any real advantage to the Three Broomsticks?

Sirius says that it would be harder to be overheard in there, but I think that's stupid because more than one person would be suspicious of a large group of kids having meeting in a busy tavern.

Answer 1

What did Sirius think?

It's actually not at all clear that Sirius did think it was a generally better meeting place; the referenced quote is a response to an interjection by Hermione, and is Sirius commenting on the flaw of one specific line of reasoning:

"You want to choose your meeting places more carefully," said Sirius, grinning still more broadly. "The Hog's Head, I ask you."

"Well,it was better than the Three Broomsticks!" said Hermione defensively. "That's always packed with people -"

"Which means you’d have been harder to overhear," said Sirius. "You've got a lot to learn, Hermione."

^{Order of the Phoenix Chapter 17: "Educational Decree Number Twenty-Four"}

But even if we assume that Sirius does think the Three Broomsticks is a better location, it's worth noting that he only believes this in comparison to the Hog's Head. And, in fairness, this isn't an unreasonable opinion.

The Three Broomsticks vs. The Hog's Head

The question claims that a large group of children meeting in a tavern would be suspicious, but the Three Broomsticks is no stranger to Hogwarts students; as we learn in Goblet of Fire:

The Three Broomsticks was packed, mainly with Hogwarts students enjoying their free afternoon, but also with a variety of magical people Harry rarely saw anywhere else.

^{Goblet of Fire Chapter 19: "The Hungarian Horntail"}

The Hog's Head, on the other hand, is a dive, practically empty, and not often visited by students:

I've told the others to meet us in the Hog's Head, that other pub, you know the one, it's not on the main road. I think it's a bit... you know... dodgy... but students don't normally go in there, so I don't think we'll be overheard."

[...]

It was not at all like the Three Broomsticks, whose large bar gave an impression of gleaming warmth and cleanliness. The Hog’s Head bar comprised one small, dingy and very dirty room that smelled strongly of something that might have been goats. The bay windows were so encrusted with grime that very little daylight could permeate the room, which was lit instead with the stubs of candles sitting on rough wooden tables. The floor seemed at first glance to be compressed earth, though as Harry stepped on to it he realized that there was stone beneath what seemed to be the accumulated filth of centuries.

[...]

There was a man at the bar whose whole head was wrapped in dirty grey bandages, though he was still managing to gulp endless glasses of some smoking, fiery substance through a slit over his mouth; two figures shrouded in hoods sat at a table in one of the windows; Harry might have thought them Dementors if they had not been talking in strong Yorkshire accents, and in a shadowy corner beside the fireplace sat a witch with a thick, black veil that fell to her toes. They could just see the tip of her nose because it caused the veil to protrude slightly.

^{Order of the Phoenix Chapter 16: "In the Hog's Head"}

Although a large meeting of youth in any location may be cause for suspicion, it certainly seems less suspicious for them to meet in a known student hang-out, rather than a dingy, out-of-the-way pub, frequented by people like Mundungus Fletcher.