Why Morrelonomicon is better than Athene's on basically every champion

This article represents the opinion of the author and not necessarely that of Team Dignitas.

In the gigantic season 3 patch, we saw the following changes to Athene's Unholy Grail:

New recipe: Fiendish Codex + Chalice of Harmony
Removed Amplifying Tome from the recipe.
Item cost reduced to 2800 from 2950.
Combine cost increased to 920 from 500.
Ability power reduced to 60 from 90.

Since then, we've seen Athene's popularity go from one of the most bought AP starting items in the game, down to being bought in only 4% of all games. (Source: Lolking.net) On the other hand, ever since Season 3, Morellonomicon, (Originally Morello's Evil Tome) has had a surprising growth from being an untouched item to a huge surge in popularity from the following changes:

Morello's Evil Tome has been renamed to Morellonomicon.
Item cost reduced to 2200 from 2330.
Combine cost reduced to 435 from 440.
Cooldown reduction is no longer unique.
Active effect removed and replaced with a passive effect.

So what's the deal with these two items? They're both items that build out of common AP starter items, are relatively cheap, and give mana regen, Cooldown Reduction, and the all important Ability Power. So why does Morellonimicon win? Well, in terms of base stats, Morellonimicon gives an extra 15 Ability Power, but Athene's wins through giving way more Mana Regeneration, and also some nice Magic resistance, and those two stats are really important for the mid lane. In addition, both items give some nice passives, but neither are really able to get a price put on them, but they both offer different advantages and playing styles. It's worth noting that both items are cost efficient even without the passives.

So again, why does Morellonomicon win? Well, in terms of the items that its built out of, Morellonomicon wins. The items are cheaper, and more importantly, both give Ability Power and either CDR or Gp5. With Athene's on the other hand, you'll pick up the Chalice of Harmony first, and that lets you spam spells, sure, but it isn't a scary item to lane against, it just lets you farm, while the same is not true with Morellonomicon. 

The biggest thing in advantage of Athene's though is mana regeneration. Well, personally, I started running mana regen yellows to make up for this, and I haven't had any major problems. Rod of Ages or Morellonimicon both seem to be substituting this item ever since the nerfs, and with the new Tear of the Goddess, its even less needed as champions like Anivia and Nidalee who were once dependent on Athene's now have another source of mana with Tear, and can get the CDR and more AP through Morellonomicon.

Finally, Morellonomicon is 400 gold cheaper, and who doesn't love that? So, in conclusion, Morellonomicon is just kind of better, especially in conjunction with the new Tear of the Goddess, and with Athene's no longer being the powerhouse it once was, alternatives are stronger. So use this information as you will, and good luck on the Fields of Justice Summoners!