>>16988404the difference is 15 at level 50. IVs are doled out until you get to 100, where the 31st one will be or has already been given out.
and to answer OP's question, it's the difference between going first, dying, surviving, or not being able to do anything
a reuniclus with some speed IVs will go after a rhyperior with 0 IVs in speed.
Also, having 0 attack IVs is important: the amount of damage you take from confusion and foul play is based off of your own attack stat, so if you're a special sweeper having 0 IVs in attack will minimize the amount of damage you take from, whereas having 31 IVs in attack means you'll take a ton more damage
