You find 3 burners enough?
And in general, what makes Weber the "best"? Longevity? Reliability? Or is it more the name...?
That. Speak to anyone that uses anything else, they need to buy a new one after 5-10 years.
I have had BBQ's with 10 people and it was enough. If you went up to like 20-30, you'd probably need something bigger.
Sounds good then. Room for 10 is far more than enough for me.
Cooking/grilling area is one thing. # of burners and BTU's is another. The ratio is not particularly well aligned across different grills. Even if the cooking area is big enough to barbecue for 10, the # of burners and BTU's may make the grill underheated, or unevenly heated, etc. That's the kind of info you'll see in professional reviews.
If you're looking for an alternative to Weber, check out Onward Manufacturing. Their Broil-Mate brand can be found at Home Depot, and Broil King at Lowes for starters. They're consistently ranked right up there with Weber, and they're generally slightly cheaper (still close to Weber than Char-Broil and it's ilk though). I paid around than $450 (after tax and 10% off) for a Broil King Signet 20 from Lowes, plus around $50 for its cover on Amazon. I'm very happy with it so far, 18 months or so in.