Mages want to know: "Which is better for me to get?"

It is an incredibly complex question, though.  For example, the answer depends on your spec, the length of the the fight you will be in, the enemy target (bosses have a higher resist rate than non-bosses), your current levels...and so much more.

It's amusing to watch the discussions on the WoW forums to see some 10-year-old with the need to prove himself talk about how uber he is and that he knows that Spirit is really all you need because he has 1000 spirit stacked and can take down Hogger with a single Arcane Explosion.  OK...I exaggerate a bit, but you do see the argument back and forth: "HIT CAP", "CRIT IS ALL THAT MATTERS", "SPELL POWER FIRST"...etc.  (all in caps because I find that people that know the least about something usually yell their opinion.)

Knowing that the answer is so complex, do not lose hope!  There is an answer.

Once again, I defer to the awesome goodness that is RAWR.

If you don't know what RAWR is, you haven't been reading here very long.   It's a free tool that has built in all the calculations and forumlas that are needed to determine your damage output.  Every possible variable, from buffs, fight duration, spec, spell rotation, gear, etc, are taken into account.

So...if you want to know how much Hit vs. Crit is worth to YOU, do this:

1. Download RAWR.
2.  Upload your toon to it.  That brings in talent spec and gear, etc., from the Armory.
3. Tweak your toon as necessary. (maybe armory doesn't have your latest gear or you had something funky equipped when you logged out.)
4. Configure the Options tab.  This includes things like your Glyphs, the level of the target mob (83 for bosses), your level, fight duration, and what buffs you will have on you in the case of a raid.  It is important to do this step, because the bonuses that come from raid buffs have an incredible impact on your DPS and on which stat is the most valuable for you.  Also, for example, if you make the fight length too long, you might see INT creep up because you'll need the mana pool.
5. On the Comparisons section (right side), where it says Gear > Head, choose from the dropdown list (you may have to scroll down), and select 'Item Budget'.

That will give you the definitive answer as to which set is best.  It shows you how much each stat increases your DPS based on the actual details that matter.

So, ignore all those loud people with their ignorant opinions.  And don't bother confusing them with the facts...their minds are already made up.  With RAWR you can REALLY know the answer without having to guess.

Math = WIN!