If I had to choose between Windows XP and Linux, I would go Linux, but not Ubuntu - just seems toy-like. Way back in the day, I grew up on Irix (anyone remember that?) Beside that, I ran Red Hat with the CDE GUI, which I loved and made it almost a seamless transition between Irix and Linux.
If Windows 7 was in the mix, I would probably have to lean to windows 7 over Linux. It is a decent OS and was decently stable. Now, I am not the average user, in that I paid attention to what I was doing, where I was going and I took care of how I used the machine. However this is true of any computer I use. I am stuck on XP at work and have been on the same image for well over a year now with no issues.
Generally, I have found in the role I play at work, if a person has continuous issues with one OS, they will have similar issues with any OS.