Re: EV training HP vs. defenses?
Depends on the poke. For example giving a Blissey 252 HP EVs boosts the stat by 64, which is about a 10% rise from the unboosted stat. Conversly maxing out it's defence stat goes from 66 to 130- almost a 100% increase. Conversly other pokes have a high Def/SpDef stat while the HP is lower, making HP a more substantial boost in survivability.
Likewise it depends on the role of the poke. If you want a wall dedicated to a single side of the spectrum, odds are maxing out both HP and the respective defense is the way to go (Unless, going back to Blissey again, one of the stats is already so massive that the EVs won't make a difference and are better invested elsewhere). Pokes that to tank both sides usually want a heavy investment in HP before splitting any available EVs between the defences.
Check the smogon strategy 'dex for sets that match what you want to attempt. Most sets have had their EVs calculated for maximum effectiveness, and you can taylor them from there.
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