wireless is more flexible but has security issues to be addressed.
cat5 is the fastest but has to be planned for all login points.
homeplug is susceptible to mains iterference and in the UK where the distribution is 3 phase then every 3rd house in a street is on the same phase so again there is a possible security/interference risk
So for best performance and security i would opt for the less flexible cat5.
The HomePlug option looks fantastic for retrofit, though.
The dedicated (CAT5) cable approach does seem the best bet.
Merely distributing audio and A-V is the easy part. How to manage the content sensibly when it arrives is the trickier part. Assuming speakers in every room as a starting point, Wiselan provides a wall-mounted audio controller (typically sited next to the light switch) with standard controls (play, skip, rewind, etc.). Nexus offers a remote for each room - letting you operate the remote sources (DVD player, TV, CD player, etc.) via an Infra-Red uplink. Think how annoying it could be for each of the teenagers in the house to be able to switch the main lounge TV from their rooms!
What works best for integrating Music, TV, A-V, Internet and Telephone (plus any other electronic services) in the home?
The three main contenders seem to be:
Structured wiring multi-room audio and video distribution system using industry standard CAT5 (or co-ax) cable e.g.
Wiselan http://www.wiselan.com/homecabling.htm
NEXUS http://www.wowlighting.co.uk/audio_video.htm
HomePlug (networking via the existing electrical sockets and cabling) e.g. Devolo Dlan http://www.devolo.co.uk/uk_EN/spezial/flashstart.html
Wireless networking
e.g. Rimax 5.8GHz Audio Video Sender & Receiver http://www.rmxdirect.co.uk/product_info.php/products_id/98?osCsid=c0f42db2dafacd067faf3d5b5ef070ac
Sonos Wireless Music 2 Zone Package with Speakers http://www.stylishautomation.com/category_Wireless_Audio_Distribution_9.aspx