Which is the superior option for a Wizard character: A familiar that gives a bonus Alertness feat and a sizable skill or save bonus, or a bonded object that allows the casting of an additional spell per day directly from the wizard's book?
Generally familiar is preferred because of you lose a familiar, you pay money. If you lose a bonded object, then you get HUGE spellcasting penalties. Plus you get a friend that will always love you despite charisma dumping...
I think the familiar is probably the better option (particularly if you take a +4 initiative boosting familiar) but I personally prefer not to have to deal with a pet.
Something to keep in mind is that a bonded object can be a free magic item at low levels. You also always count as having the relevant Item Creation Feat for enhancing your bonded object.
Ultimately it comes down to your preference as a player though :)
Familiar is stronger. Bonded item is much easier to use.
Familiar
-2 feat equivalent abilities
-extra set of actions per round
-roll 2x on many skill checks
Item bond
-1 spell per day
-money from saved enchanting costs
-dont have to keep leveling a critter
I would also note that losing a bonded object isn't that big of an issue for several reasons
1. Concentration checks are fairly easy to make at mid-high level
2. Rings, the best option, are really really hard to break or lose
3. You are already having to defend a book. That is a bigger, more vulnerable, and more valuable target. Who cares to hit my ring which may or may not affect me when you have a spell book to burn/steal.
The two options are remarkably well balanced with each other for being so different.
The extra spell from your bonded object can be anything in your spell book - that flexibility is very powerful. But familiars, and especially wand-wielding Improved Familiars with powerful abilities, add a great deal. I've played with both, and I would be happy to do so with either option again - it really depends more on my concept of who the caster is.