If you require HD playback then go for the Popcorn as it has a better chipset (EM8634) than the Zyxel. The Zyxel looks good for SD only, as it doesnt support the majority of HD formats/codecs and doesnt have 1080p, but uses technology that is established whereas the PCH is developing all the time. If you like an active forum then the PCH has one and a good community developing new apps etc.
I imported my PCH total cost inc customs and shipping £140. If you find a problem then you will have to RMA it to USA or China but it comes back in about 3 weeks total.
The PCH brings you an internal HD (IDE 750GB), YouTube, component connection, wireless (next firmware max 20mb/s so only for SD), video jukebox, stream from NAS, SMB/NFS/FTP, does 1080p, etc...
The PCH will take you longer to get to know as there are a hell of a lot of features etc. but for about £30 more IMO its well worth it.