There are numerous factor in determining which operating system is better but it all boils down to one fact - does it fit your needs?

If it does, considering all factors (hardware support, applications, speed, maintainability, etc) can help you get a more educated answer to your question.

On a more objective note, it seems that Ubuntu (and specifically Xubuntu which is lighter than Ubuntu) can run better on older hardware which is almost an impossible task (depending on how old the hardware is) to accomplish on Vista (if possible at all).

So in that sense, on older hardware that cannot run Vista, Ubuntu 7.10 (and more specifically Xubuntu) is better than Vista.