The larger 20GB ZEN, is a little bigger than the MICRO, has a slightly different button layout on the front panel, and also does not have the FM radio function. The battery doesnt last anywhere near as long as the micro either as it is HDD based and not solid state memory (as the micro has). If your main interest in going for the 20GB version is purely for the size, I personally wouldnt recommend it as i don't really think anyone needs to carry about 20GB of music with them, 5GB should be enough for anyone - it is easy enough to swap tracks to and from the device as necesarry (I don't even have 20GB on my PC and I've been encoding music for about 7 years, I have 18.96GB). I prefer the longer battery life of the 5GB micro, compared to the capacity of it's big brother, and as for ipod's....forget them, they're for sheep who only follow the masses with the latest trend and they have limited compatability with diffewring music formats.