Spell hit vs. spell penetration

Spell Hit and Spell Penetration -- what's the difference? On the surface, they both seem to decrease the chance for your spells to be resisted. So what makes them different?

The fact that they do the same thing (more or less) in different ways.

Let's take a look at Spell Hit (SH) first. The more SH you have, the less your spells are likely to be resisted. Unfortunately, this is capped at 99% (according to WoWWiki), which means that there is always a 1% chance that your spell will be resisted. We're not going to go into the actual mechanics of SH here -- this post is just about the difference between SH and SP (Spell Penetration).

Now let's look at SP. Spell Penetration reduces the target's resistance to your spells. Sounds an awful lot like SH, no? Maybe. But it's not reducing the target's chance to resist your spells, it's reducing your target's resistance. You know, that stat that can be buffed with various types of resist gear, Paladin auras, Mark of the Wild, etc. This is where SP differs from SH -- it only works on targets that have resistances, and won't reduce resistance below zero (again, according to WoWWiki).

This means that if you're a Frost Mage with 70 spell penetration facing off against a Paladin with Frost Resist Aura up, you're essentially negating his Aura when using your frost spells.

You can get your SP stat up with gear, enchants and gems. It's important to note that if your target's resistance is zero, your SP stat is wasted, so make sure you don't neglect your other stats in favor of Spell Penetration!

http://wow-addicts-anonymous.blogspot.com/2007/09/spell-hit-vs-spell-penetration.html