I belive that PLC-BUS is a new proprietory standard that is coming out of China, with the hardware being different to X10 but being housed in the same cases as the new "2G" appliance modules.
However, its not know how far the standard will propegate and you may find yourself reverting back to standard X10 modules for things that are not available in PLC-BUS.
I would urge you to try X10 before you make your decisions, as it isnt too expensive and you can always re-sell your modules if you are not happy with performance.
In our house, which is a 4 bedroom detached built in the 60s with some older style wiring (wire fuses rather than RCDs, etc) there have never been any issues with reliability, which I had expected due to the older wiring.
The slight delay when processing can be a little annoying at times, but most of the time you have lights and appliances running on macros, so a half-second delay does not even get noticed once the system is up and running.
If you do go with PLC-BUS, let us know how you get on!