And there is no easy answer I'm afraid, because as you have pointed out, some software can manage updating it's own installation, whilst others recommend uninstalling the old before installing the new.
I don't use utilities like CNET's Watch List or TechTracker. To be blunt, I don't entirely trust them.
In all my years using Windows based PCs, I have only once updated a driver. If it is working for me and my machine, then I don't need to update it.
But software applications are different. Many applications attempt to set a process or service in the system that continuously checks for updates. Or it sets itself to "Load at Startup" so that the application is always running with an open internet connection. Two I can think of are Google, (Chrome, Toolbars, Google Earth, etc), and Real Player. I fight like heck to remove those updaters or from startup as I don't want my internet connection continuously wasted by updater accessors, nor do I want 'even more' services or processes running in the background.
And yet, I allow others to continuously check for themselves, like my ZoneAlarm security suite, my Firefox browser and add-ons. Since they are being used all the time I need to know they are always up to date. I don't mean ZA's virus and spyware definitions. They must always be automatically updated. But I mean any application updates.
Both of those I mentioned work differently. Firefox will allow itself to be 'application updated' without uninstalling, but ZA will usually have to uninstall itself before installing a new version application.
At the end of the day I have to trust updaters like these to know what they are doing. But if I am not sure, I will go to the web sites for more information.
Anything else I have I will keep an eye open for "Tech News" for vulnerabilities and such. For example, I keep a close eye on Adobe Flash news. Adobe is notorious for vulnerabilities and not closing them in a timeous manner, so I look for news about new versions.
It's difficult.
Mark
Something that I've wondered about is how to consistently handle program updates that we download. This is often the case when CNET notifies me that a new version of a program on my "Watch List" is available.
Once we download the file with the newest version - usually an .exe file - how do we know whether to:
(1) Double-click the new .exe file to directly load it *over* the existing version? OR
(2) Remove the old program file(s) first, and then load the new version?
Is there any way to know which program updates can replace their existing versions and which updates should be clean installs? Thanks.

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