Where are you located? That will determine what is available.
Z-Wave happens to be available in both North American and European versions and one or the other usually works in other places around the world - it depends on local regulations on frequencies, etc.
I haven't looked at Z-Wave in any depth since its introduction so my comments may be outdated.
It costs quite a bit more than X-10 and only a few companies provide software to control the various serial and USB interfaces. The mesh network requires strict adherence to rules. Adding a node requires retraining the entire network, removing a node improperly creates problems. Defective nodes (that have in effect removed themselves improperly) create big problems. Range is short so modules need to be rather closely spaced (~20' MAX IIRC). The number of hops is limited. The combination of short range with limited hops means you may run out of hops before you run out of real estate.
If you want to write your own software, the SDK only costs $3500.