Interesting read and unfortunately I am too little too late. I did a substantial amount of buckshot testing a few years ago of offerings from Remington, Federal, and Winchester. My object was to find a load which had a serviceable pattern at both contact distance and held minute of pizza box out to twenty yards. The test gun was a 14" Mossberg 590 shockwave firearm. I found that Federal premium 000 in 3" and 2¾" worked out well. Also the Winchester #1 Buckshot was a stellar performer and was what I ultimately went with. My secondary load is Federal Premium 3" 000. I believe that #1 Buck is better over distance than any of the 0, 00, or 000B for pattern retention and has better penetration than 4B and 00B. I Believe there is not a big difference in .33 and .30. I feel there is difference in .30 and .24/.25. I also noted that .36 shot had a tendency to bounce up off the ground at 20 to 25 yards when fired at a downward angle and clip branches out of trees on the regular. I found that the Remington produced the largest patterns of all standard buffered buckshots tested save the Kent economy buckshot which I hold in reserve for high volume use. The most blown out pattern I saw was from the Winchester offering of the supreme double x buckshot where they have increased the velocity from traditional speeds to 1450fps. These patterns expanded rapidly and in my opinion would be good for close range use where the user wanted a bigger pattern as was not going to shoot beyond 20 yards.
Stock numbers for Winchester: XB121 and SB1200.
Stock number for Federal: currently unavailable in 2¾"