Looking around at some posts talking about stat weights and priorities, it seems like 1 MND = ~3 Crit Rate = ~5 Determination. Not sure about the weight of Spell Speed (some posts have said it's about equal to Determination).
And 1 Weapon Damage is typically worth about 8 points of your main stat for any class (MND, in the case of Scholars).

Here are the positive comparative differences in DPS-related stats between the Omnilex and the Mogbook:
Magnificent Mogbook = +31 Crit
Omnilex = +1 Weapon Damage, +3 MND, +16 Det, +11 Spell Speed

Using the weights listed above, the 31 Crit gained from the Mogbook is equivalent to about 10 Mind.
Using the weights listed above, the 1 Weapon Damage, 3 MND, 16 Det and 11 Spell Speed gained from the Omnilex is equivalent to about 14 Mind. Plus 11 Spell Speed and 3 Vitality.

The difference between the two weapons equates to a few Mind and a few Vitality; nothing particularly game-changing. If you're strictly interested in having the best i80 Weapon in terms of healing-per-second, then it looks like the Omnilex is the one you want. The Mogbook looks and sounds pretty darn cute, though, and the actual difference in healing-per-second between Omnilex and Mogbook is relatively small.