For me the Sony's advantages (in approximate rank order of importance):
-battery life (#1 most important issue for me by far)
-SD card
-audio quality (Hi-res, DSEE, Bluetooth apt-X - although there are rumors the Moto X might also support apt-X I can't find any official confirmation of this)
-camera performance
-smaller size/weight
-waterproof (Moto X is only water resistant, meaning it may or may not survive accidental drop into the bath tub)
-More LTE bands (my Z3 model D5803 gets 700/800/850/900/1700/1800/1900/2100/2600 but the U.S. model (D5833) has fewer LTE bands: 700 / 850 / 900 / 1800 / 2100 / 2600. In comparison Moto X only has only three: 800 / 1800 / 2600)
-dedicated camera button
-glove mode
-FM radio
-PS4 support (don't have a PS any more so not really an advantage for me, but maybe someday...)
Moto X's advantages (again, roughly in my rank order of importance):
-ergonomics, in-hand feel (subjective but it seems that there is a general consensus that this phone has great ergonomics although perhaps not quite as good as last year's smaller version)
-active display
-handsfree software
-design/materials customizations
-1080p and bigger screen (but this also makes the phone bigger/heavier, so there is a tradeoff)
-rapid charge (this is only really useful if you actually need to charge your phone during the day, which you don't need to do with the Z3. the fact that Moto had to include this feature is a sign of weakness)
Overall, I'm sure the Moto X (and Droid Turbo if you're on Verizon would appear to be even better) is a better option for many people than the Z3, but the Z3 ticked more of my boxes.
-battery life (#1 most important issue for me by far)
-SD card
-audio quality (Hi-res, DSEE, Bluetooth apt-X - although there are rumors the Moto X might also support apt-X I can't find any official confirmation of this)
-camera performance
-smaller size/weight
-waterproof (Moto X is only water resistant, meaning it may or may not survive accidental drop into the bath tub)
-More LTE bands (my Z3 model D5803 gets 700/800/850/900/1700/1800/1900/2100/2600 but the U.S. model (D5833) has fewer LTE bands: 700 / 850 / 900 / 1800 / 2100 / 2600. In comparison Moto X only has only three: 800 / 1800 / 2600)
-dedicated camera button
-glove mode
-FM radio
-PS4 support (don't have a PS any more so not really an advantage for me, but maybe someday...)
Moto X's advantages (again, roughly in my rank order of importance):
-ergonomics, in-hand feel (subjective but it seems that there is a general consensus that this phone has great ergonomics although perhaps not quite as good as last year's smaller version)
-active display
-handsfree software
-design/materials customizations
-1080p and bigger screen (but this also makes the phone bigger/heavier, so there is a tradeoff)
-rapid charge (this is only really useful if you actually need to charge your phone during the day, which you don't need to do with the Z3. the fact that Moto had to include this feature is a sign of weakness)
Overall, I'm sure the Moto X (and Droid Turbo if you're on Verizon would appear to be even better) is a better option for many people than the Z3, but the Z3 ticked more of my boxes.