I am pretty old school, but the 3d6 method has so variation. It also forces the player into something different from what he wants to play, if he gets several bad rolls (pretty easy to do, actually). 4d6 drop lowest has the same problem.
Now, when I was first shown point-buy, I didn't like it, because I was used to rolling for stats, and the idea that someone could just pick an 18 seemed wrong. But lately? I have grown more and more enamored of the 20- and 25-point buy system with the Pathfinder values. You can build a solid character on 20-points and a very good character on 25-points.
For example: Someone in the group has their heart set on playing a swashbuckling rogue. They need Str, Dex, Con, Int, and Char; not necessarily extravagant scores in those abilities, but they all have a reason.
With 20-point buy, that character could get the following (before racial modifiers)
Strength 14 (5 points)
Dexterity 14 (5 points)
Constitution 12 (2 points)
Intelligence 12 (2 points)
Wisdom 11 (1 points)
Charisma (14 (5 points)
Is he a super-uber character that is going to overpower at 1st-level? No, but he has no real weakness, and it fits his Errol Flynn concept. Strong, dextrous, smart, and witty, and able to take some punches.
Now, let's look at rolling for that same character concept. I won't have him assign his stats in order, either. I'll even let him roll seven times, and keep the six highest. Fair?
3d6 ⇒ (5, 6, 1) = 12 =12
3d6 ⇒ (4, 4, 5) = 13 =13
3d6 ⇒ (3, 4, 1) = 8 =8
3d6 ⇒ (1, 5, 1) = 7 =7
3d6 ⇒ (5, 4, 3) = 12 =12
3d6 ⇒ (6, 3, 3) = 12 =12
3d6 ⇒ (4, 4, 3) = 11 =11
We end up with 13; 12; 12; 12; 11; 8, for an 8-point buy.
Strength 13 (3 points)
Dexterity 12 (2 points)
Constitution 11 (1 point)
Intelligence 12 (2 points)
Wisdom 8 (-2 points)
Charisma 12 (2 points)
Is it playable? Sure. Did I get good rolls? Yes. But I could have just as easily gotten horrible rolls or a bunch of very high scores. In my mind, point-buy just makes things easier by letting your players choose their own path, instead of having to play what the dice say. It is their character, let them make it how they want it to be.
And that's all I've got to say about that.
Master Arminas