ZuneThoughts posted an interview of Andrew "bunnie" Huang (well-known for his work on hacking the security architecture of Microsoft's first-generation Xbox).

Andrew says the main factor Zune is thicker, is the larger display which has impact on this. The big battery capacity of 800 mAh has bigger volume than iPod video's (about) 400 mAh and the semi-transparent case of Zune also adds about 1-2 mm.

The interesting part is why Zune needs twice the battery of the iPod for the same playback abilities both have. Zune has some quite impressive UI effects. The reason is the CPU used, freescale's iMX31 at 533 MHz! This is a very powerful CPU comparing to 300 MHz iPod uses (plus a 150 MHz video co-processor).

And the above is the key to reveal Zune's power, keeping also in mind Microsoft is a software company. Selecting to do everything in software without dedicated co-processors like Apple, Zune has the freedom of choice in what features and codecs it can embed in the future. Andrew says this processor for example has no problem decoding H.264/AAC (the iPod's codec). So Microsoft can write software without much optimisation and buy support for codecs it doesn't own.

Of course this doesn't mean Apple's way is wrong. Only users and time can give the answer.

You can also check the full Zune chipset details .

Read the full interview on ZuneThoughts.