The linked article sums this up in the last paragraphs where it points out the #1 Buck is probably the "best" buckshot load, but that it is hard to find, and 00 Buckshot is a very close second, so that is what most of us use.
Let's put some false rumors to rest:
1. Birdshot is a good self defense load.
This is false for several reasons. The main reason is that no birdshot load will reach the required 12 inches of penetration needed for STOPPING a bad guy from whatever he is doing to threaten your life. Birdshot makes a very nasty, yet shallow wound, and will not reach the vital organs or CNS.
"Might" birdshot work? Sure. But why depend on "might" when "better" is available.
Use birdshot for little birds. Use buckshot for bad guys.
2. Buckshot penetrates too much and will go through walls in my home.
Sure it will. Any load that will STOP a bad guy, will also penetrate several interior walls, as I proved here: Rifles, Shotguns, and Walls
Until someone invents a phaser, like on Star Trek, any load that will STOP a bad guy will also penetrate several walls.
3. Any buckshot will work about the same.
While any buckshot is better than birdshot, the larger the buckshot pellets, the more they will weigh, and the more they will penetrate. The #4 Buckshot I measured is the "minimal" buckshot load, and will barely meet the penetration standards. Some folks like it, and some police departments even issue it, but it is the smallest buckshot and will penetrate the least. Larger is better, and 00 is preferred.
4. Getting shot with a load of 00 buckshot is like getting shot 9 times with a handgun.
Each 00 pellet weighed about 60 grains. No normal handgun round shoots a bullet that light in weight. A .32 ACP round has a 71 grain bullet traveling at 900 fps. That is the lightest "common" handgun bullet around. But it is only doing 900 fps.
The 00 buckshot pellets weigh 60 grains, but are doing 1,325 fps. There is no comparison between the two.
And the shotgun pellets all hit the target at around the same time. Very effective.