I promised in my last post that I'd run a more detailed test and get back to you ...
My wife's Linux laptop is an IBM/Lenovo ThinkPad T43 (model 1875M2U, purchased in early 2005.) It has an Intel Centrino CPU (1.86 GHz) with 512 MB memory. She is running a generic install of Fedora 10, with all the default startup processes left running. This is how the system would be set up if any non-expert user had installed it. More importantly, it's what my Linux laptop would have looked like if I could run Linux at work.
My Windows laptop is a Dell Latitude D430 (purchased in late 2007 or early 2008) so it's about 3 years newer than my wife's laptop. It has an Intel Core2 CPU (1.20GHz) with 2 GB memory. I'm running Windows XP Professional with Service Pack 3, installed for me by our desktop support folks at work, using the standard "manager laptop" image. This is exactly the same image that every other manager at work is using. I don't know if any of the usual startup services have been disabled.
In short: the Linux laptop is about 3 years older than the Windows laptop. The Core2 CPU has a slightly different design than the Centrino, so you can't directly compare GHz speeds here.
At work, I'm a manager, so I typically only run things like Office and Firefox to do my work. Every morning, my startup routine is the same: boot my laptop, start Firefox, login to our webmail system and check for any urgent emails. I also login to our web-based calendar system to look at my meetings for the day. So it shouldn't be a surprise that I measure the time by which I can start doing work by how long it takes to boot my laptop and run Firefox.
This afternoon, I ran a side-by-side boot test, using a simple "minute:second" stopwatch to see how long it took to boot each system. The results are interesting:
Powering on both laptops simultaneously (a "cold boot") it took about the same amount of time for both to prompt me for the hard drive encryption password. Windows was ready for me a fraction of a second earlier, so I typed my username / password there first before typing my passphrase into the Linux laptop.
Windows felt like it was taking a long time to boot. I've previously discussed how you never really know if you've launched a program or opened a document in Windows, or merely selected it. While booting, Windows doesn't tell you what it's doing. You just get the "cylon" progress bar, so at least you know Windows hasn't hung. (Linux has a neat little progress bar while it's booting.)
Surprisingly, both laptops also prompted for login at about the same time (1:15 after boot.) But Windows was deceiving; after pressing ctrl-alt-del to start the login process, it took several seconds before the username / password dialog box came up. As a result, I had already typed in my username and password on the Linux laptop by the time Windows was really ready for me.
As soon as either laptop presented me with my desktop, I immediately launched Firefox. The Linux laptop brought up Firefox and presented me with a web page (2:10) much faster than Windows (3:07). So, about a minute faster.
As a point of interest, I was able login to our webmail system at work, read an email, and delete it in the extra time it took Windows to start Firefox. And that's on a laptop that's 3 years older.