Windows 7: Log Off/On versus Reboot?

Depending on particular circumstances, I often Reboot before I install or uninstall programs. But for things like VLC updates (or other items found by Avast that need updated), I just Log Off then back On before updating.

So is there any 'real' difference between Logging Off/On versus a full Reboot on stuff like this? Not only is Logging Off/On a lot quicker, it has to be less wear and tear on the system.

Edit:
PS: I forgot to mention that after doing things, like the 4 or 5 updates Avast recommended, I still do a full Reboot (like now :) )

As I understand things, some updates (whether it be a Windows Update or some other software/application update) might be tied in to system files. As long as those files are actively being used, they can't be successfully updated. That's when a reboot rather than a log off is required. I think this article gives a much better explanation of when/why a reboot might be needed.

Why Do Application Installs Make You Reboot and Close Other Apps?

A reboot involves the complete shutting down and restarting of the Windows system. A logoff and logon cycle simply shuts down and restarts the user session. The Windows system and system services will continue to run without interruption. Updates involving system software, typical of security software updates, will often require a reboot. Many system configuration changes will not take effect until a reboot. Microsoft is working to reduce the need for reboots but there is still a ways to go. Usually the update, whether it be system or application, will specify what should be done. If a reboot is requested you should do so. It may not be strictly necessary but you have no way of knowing that for certain.

Thanks for the tips and suggestions :)

There`s no reason to do any of that unless Windows tells you to. :)