>>23490324It's very match-up based, with so many threats in the tier you can't prepare for everything and you'll occassionally just get rolled by something.
For example, if you run
Infernape/Clefable/Gyarados/Rhyperior/Celebi/MZor
You may have a decent match-up versus some top threats like Lando-I, Bisharp, Keldeo, and Mega Metagross, but you get rolled by Crawdaunt, Mega Gyarados, and Fire Blast Altaria. You can run Chesnaught over Infernape and beat the Water/Darks, but then Mew rolls you.
Pure Offense also struggles with match-up thanks to shit like Mega Manectric that you usually have to play around or just get fucked. Balance is the most consistent style because it gives you the most options to deal with these threats, and is just a generally good style. Thus, having a good match-up against most balance teams is nice.