We use both Vera and SmartThings over two sites, covering about 100 devices. The Vera Edge controller has been 100% reliable, but has required a PLEG plugin (allows more complex automations with variables, conditionals, timers etc. to handle security system integration, 9 stats, various zwave devices and automated windows. Vera can handle automations standalone, so no web connection is required..although you'll want it connected to program.
SmartThings is another option that can be a bit flaky at times, but is much easier to deal with. It also handles both ZigBee and Zwave radios. Unlike Vera, a solid web connection is required. It very much is biased to smartphone management, although a web based system gives you access to tweak, design your own apps, troubleshoot etc. Do a search for on my recent threads and you'll find plenty of info.
The basics are this: ZigBee and zwave are low power radio devices that create their own mesh network. This addresses their low range challenges, as most plug in (or constantly powered) devices can serve as relays for neighbour devices. battery powered devices usually do not serve as relays. You need a hub which is used at first to "include" the device. The hub also serves a role in managing the mesh network. The real power of these devices though comes in managing your devices via automations. We've cut up to 38% power consumption at two sites (one home, the other business) by creating automations that:
- enable whole building night pre-cooling
- turn off AC when zones windows are opened
- manages 5 air handlers and two HRVs based on presence, and security system so that we're running this equipment only when required.
- cut power to computers when security is armed
- turn off more or less our entire house when phone's leave the area.
- manage lighting on and off at home
- dim lights as appropriate based on outdoor ambient light.
- program locks based on time and day so cleaner for example can only access at specific times, and our iOS devices are notified when that code is used.
- manage my garage door so if left open I am notified and can close it remotely.
- handles garage "disco" lighting when my kids are partying in there

etc.
The hubs and the automations they host are key to all of this. When a security system and all of its sensors are seen by a hub, along with thermostats and zwave/ZigBee devices the path to efficiency becomes a lot easier.