I can find Z-Wave locks stocked at stores all over town. When it comes to the exact same lock running Zigbee not so much. I’m referring to the Kwikset SmartCode 910 series locks in particular but in general it appears locks are predominantly Z-Wave. Why is that?
Is it just me or is Z-Wave more popular when it comes to locks as opposed to Zigbee?
I think the main reason for this is that Z-wave locks in general are less likely to suffer from interference since they operate on 900mHz. If you have a lot of interference near your door lock you can’t move it unlike other devices. Z-Wave locks also had greater acceptance in the beginning.
I however actually use a ZigBee Yale 240 lock and have never had any issues with it.
I agree with @jhamstead . I like zigbee for many things, particularly battery-operated sensors, but it is subject to interference from Wi-Fi, which zwave is not. Consequently it can be challenging to deploy zigbee devices in fixed location uses like locks and motorized window coverings. Professional installers who have the tools and training to deal with this type of interference can usually find a way to make it work, but it’s not as suitable for DIY implementations.
At my house, we had a problem with boosted Wi-Fi. If we plugged in the Wi-Fi extender on the north wall, we would immediately lose contact with all the zigbee devices west of that. If we just moved the extender to the east wall, everything ran fine.
I also have an ongoing problem with the SmartThings brand arrival sensor, which is nonamplified zigbee. Most weekday afternoons between 330 and 430 or so it just goes bananas and shows itself leaving arriving leaving arriving etcetera. SmartThings support and I worked on it for several months but couldn’t find a resolution. I suspect one of my neighbors has a kid who gets home from school around that time and they have boosted Wi-Fi and it’s affecting the zigbee for the presence sensor.
If you really want a zigbee lock, you can typically get the zigbee module from the lock manufacturer, such as Yale or Kwikset.
In my case, I knew that I would have Wi-Fi cameras near the front door and I wanted to have a strong Wi-Fi signal there. For that reason, I chose a zwave lock.
But the zigbee locks are available, and you can try one and see how it works at your house. 
Here is a ZigBee Yale 240 lock. I’d recommend Yale over Kwikset.
I’ve got a GE ZigBee switch for the porch light that works okay right next to the front door. Since the switch is also a ZigBee repeater I don’t think signal is going to be a problem.
I’ll give it a shot and report back on my experience once I have it installed.
I bought a Kwikset SmartCode 910 Zigbee version model 910TRL ZBC4 L03 SMT http://www.kwikset.com/products/details/electronic-locks/910trl-zbc4-l03-smt.aspx
I have a GE 45856GE ZigBee In-Wall switch next to the door for the porch light that acts as a repeater. I’ve had the lock installed for about a week now and everything seems to be working as expected.
A couple of things to note:
You can’t manage PIN codes via the SmartThings app
SmartThings recognized the lock as a “Kwikset 5-Button Deadbolt” instead of a Kwikset SmartCode 910. Technically only the “Kwikset SmartCode 910 Contemporary” is listed as being supported which is the same lock with a different finish. Since SmartThings only recognized a generic Kwikset lock, some functionality could be missing. I can only speculate.
To answer my original question, the Zigbee version works perfectly.
I’ve been writing a DTH to make it possible to change the codes for ZigBee locks through SmartThings. It is still in its early stages but it works and can be found here.
You will also need the lock codes manager SmartApp