Was talking to Theorymon about this earlier, figured I might as well post about it. I dunno how many of you remember early DP OU, but there was a pokemon called Garchomp, and a pokemon called Swampert. Garchomp was actually defensively stronger than Swampert, and had superior speed as well. So why did people favor defensive SR Swampert sets, but disdain such sets on Garchomp? The answer is Opportunity Cost, the value of the next best alternative. The best alternative for a Swampert set was either Curse or CB, which were super situational. The best alternative for a Garchomp set was Scarf or SD, which were...good. And so, many people used Swampert for SR, but not Garchomp. In Ubers, this matters mainly in terms of Arceus. When people say an Arceus form (usually Bug/Fire/Ice) is "bad," they don't mean it's a bad Pokemon. They mean the opportunity cost of using that Arceus form is too high. The next best alternative to that form usually ends up being something like Extreme Killer or CM Ghost, which are better than those Pokemon except in niche cases. Also, Bug/Fire/Ice Arceus are hard to put on teams IMO, they aren't very self-contained, instead requiring a lot of support. I dunno, that's what I think at least.