Hibernation times: Ubuntu 10.04 vs Windows XP Home

I have two OS's installed on my netbook. I wanted to test how long it would take to go to and resume from hibernate. I think this time is an important time, because I always use hibernation on my netbook.

Computer: Compaq Mini 730eo (Atom N270 1,6 GHz with 4200 rpm harddrive)
OS 1: Windows XP Home (Service Pack 3)
OS 2: Ubuntu Netbook Remix 10.04
Scenario: One Firefox instance open that has loaded Gmail.

Time to boot computer to bootloader: 8 s. This number can be added to the below times to get the total startup time.

	Ubuntu	Windows
To hibernate	48 s	14 s
From hibernate	40 s	18 s

Why is Windows so much faster? I don't know. One guess I have is that Ubuntu saves the entire RAM to disc, including caches and buffers. But that would be rather crazy, so it is probably some other explanation.