I don't think you will get near the battery claim on any phone with medium-heavy use. That is just the way things are.
14 hours is not bad, and that still is about a full day of use if you charge it nightly.
I think the Moto X will definitely be a downgrade in terms of battery life. The Droid Maxx has a 3500 mah battery, where the Moto X has a 2200 mah battery.
They run very similar software and I would guess then you would probably get about 8 hours of heavy use out of the MotoX
I ended up getting the HTC One (the phone I've been salivating over since it first came out) and I get about 12 hours give or take easily with medium use. I bought a Mophie Juice Pack and honestly, I'm so much happier.
The Verge also notes that on their recent review of both the Maxx and the Ultra: battery lifeisn't nearly as good as the firm advertises, nor up to par with their previous Maxx-series Droids.