Insteon will be more reliable as it's immune to wireless interference. Two things can affect remote signaling, wireless interference, and powerline interference (for instance, from improper grounding, or an old refrigerator). Since it's rare to have both at once, Insteon covers both angles, and can use either powerline or wireless interchangeably. Z-Wave may have a better software protocol, but for your use, you'd never notice the difference.
Founder for the CastleOS Home Automation System, featuring Kinect integration www.CastleOS.com