Dudunsparce is subjectively the funniest pokemon of all time and it has 2 forms, which are functionally identical... Or are they?
You see, despite having identical stats, typing and abilities, there is a very slight difference between them: weight. Dudunsparce 2 segment weighs 39.2kg and 3 segment weighs 47.4kg. dudunsparce also learns the move heavy slam, which does more damage the heavier you are than your opponent, so 3 segment being heavier than 2 segment means it will be dealing slightly more damage again SOME opposing pokemon. Dudunsparce being heavier also means it takes less damage from opposing heavy slams!
You may argue that dudunsparce 3 segment is worse because it's higher weight means it takes more damage from low kick/grass knot, but that just isn't the case. Unlike heavy slam, low kick/grass knot deal damage purely on the opponents weight, which is why in Ubers some Koraidon use low kick (despite being an absolute Chonker). If the opponent weighs anywhere between 25kg and 49.9kg, grass knot/low kick have a base power of 60. Both dudunsparce forms are within this range, so they will both be hit with a 60BP low kick/grass knot
In conclusion, Dudunsparce 3 segment being heavier than Dudunsparce 2 segment means it deals more/takes less damage from heavy slam, while also not taking more damage from low kick/grass knot, thus making it the objectively better form of the two
You see, despite having identical stats, typing and abilities, there is a very slight difference between them: weight. Dudunsparce 2 segment weighs 39.2kg and 3 segment weighs 47.4kg. dudunsparce also learns the move heavy slam, which does more damage the heavier you are than your opponent, so 3 segment being heavier than 2 segment means it will be dealing slightly more damage again SOME opposing pokemon. Dudunsparce being heavier also means it takes less damage from opposing heavy slams!
You may argue that dudunsparce 3 segment is worse because it's higher weight means it takes more damage from low kick/grass knot, but that just isn't the case. Unlike heavy slam, low kick/grass knot deal damage purely on the opponents weight, which is why in Ubers some Koraidon use low kick (despite being an absolute Chonker). If the opponent weighs anywhere between 25kg and 49.9kg, grass knot/low kick have a base power of 60. Both dudunsparce forms are within this range, so they will both be hit with a 60BP low kick/grass knot
In conclusion, Dudunsparce 3 segment being heavier than Dudunsparce 2 segment means it deals more/takes less damage from heavy slam, while also not taking more damage from low kick/grass knot, thus making it the objectively better form of the two