How about we collect what we already know:
- both devices use the same display technology (E Ink)
- the iLiad screen is bigger (8.1") than the Sony Reader screen (6") -> Q: is battery negatively influenced by a bigger E Ink screen?
- the iLiad offers 16 gray levels, the Sony only 4 -> Q: is the battery negatively influenced by the number of gray levels?
- both devices run on Linux -> Q: kernel versions?, loaded modules?
- the iLiad has WiFi 802.11b -> Q: in power-savings mode, can it be completely turned off?
- the iLiad uses a WaCom Penabled touchscreen ->Q: in power-savings mode, can it be completely turned off? By how much does it affect battery life?
- the iLiad uses a Li-ion 1100mAh battery -> Q: what is the capacity of the battery used by the Sony?
- the CPU of the iLiad is an Intel XScale 400MHz PXA 255 -> Q: in power-savings mode, CPU could be throttled down to 200MHz, is this already working with the latest software? What CPU does the Sony use?