Inexpensive buckshot loads (S&B, Rio Royal etc) generally have unplated soft lead alloy pellets, no shot cups or collars, fiber wads, roll crimps with over-shot cards etc. This means the pellets distort when 'crunched' by the powder charge going off upon firing, distort more going through the forcing cone, bore and choke, and get pushed out the muzzle with 'flats' on them that cause them to divert from a straight flight path. In some cases the over-shot card distorts patterns from the front while the wad being pushed into the pellets from the rear tends to scatter them too.
For 'open pattern' folks, the inexpensive buckshot loads are just the ticket. Around here we reserve a certain quantity of S&B for "to whom it may concern" use in the night, should circumstances ever warrant that approach.
The more expensive loads have hard alloy pellets that are often nickel or copper plated to resist damage on firing and traveling down the bore, substantial shot cups that protect the pellets in the bore and in some cases help hold them together as they exit the muzzle, good wad columns that help soften the blow of firing and star crimps that open smoothly and don't further interfere with the pellets.
I basically quit experimenting with barrels, chokes, choke tubes and buckshot loads in 2008 when I bought my first batch of Federal 00 with FliteControl wads. Since then all I've bought by way of 12 ga. serious shotgun ammo has been Federal LE127 00 and Brenneke KO rifled slugs. I still like to use open choke barrels on working shotguns, and these loads do very well out of every barrel I've tried them in so far.
ymmv of course...
Mindset - Skillset - Toolset. In that order!
Attitude and skill will get you through times of no gear, better than gear will get you through times of no attitude and no skill.