Judging by that one battle, Cynthia, at least, probably just evens out to "approximately the same difficulty"
DP: She has tough, bulky pokemon, at a high level, the Garchomp is a terror
BDSP: She has tough, bulky pokemon, with high internals and held items, the Garchomp is a terror
That video was honestly very similar to my first playthrough.
That said I don't think the same thinking will necessarily apply to the rest of the e4 or other leaders....a lot of the time it really does come down to the pokemon. 3/5ths of Aaron's team is absolutely nothing, his Heracross & Drapion will last longer & deal more damage no matter the context just because they're generally better Pokemon at a base level.
Maylene might have cool synergy, but Meditite isnt super fast and is very frail and both it & Machoke will die very quickly (in fact the "speed run" first leaker, where staravia didnt even have affeciton boosts, literally killed both like 1 wing attack each). Lucario, meanwhile, has a more "difficult" typing to deal with and better stats: bulk up or no, evs or otherwise, it's going to do better and be a greater difficulty to fight at.
I really don't want to undersell how neat the boss sets are, how there's attempts to do things there, of course. But as time goes on I do get the feeling people are kind of overselling it.
Actually it's Magikarp/Gyarados, level 100, catchable by fishing in
Nature Preserve.
A really intresting list BTW :)
Ah, you're right! I completely forgot the Nature PReserve also had that gimmick.