Radagast have blogged about how the comparison of XP and Ubuntu fares, and he is impressed by Ubuntu.
Read about it here
Windows XP and Ubuntu 6.06 were both quick to install; each install was complete in less than two hours. Windows took about twice as long as Ubuntu to install, primarily because of the additional time required to install (and update) non-OS software packages.
The largest potential problem with both operating system installations is hardware recognition (as I encountered with Windows XP). Ubuntu's use of a LiveCD is an advantage here, as it allows new users to test their system before formatting their hard drive. However, more hardware is generally supported in Windows than in Ubuntu, as many manufacturers build Windows-specific drivers (but do not make Linux drivers).