The NoStore property is used to inform proxy servers and browser that they should not store a permanent copy of the cached content by setting Cache-Control: no-store within the request header.
Duration simply specifies how long the content of the controller action should be cached, e.g. 10seconds. This will set the Cache-Control: max-age to >= 0. And also sets the Expires header to a valid timestamp.
To your initial question, no, the three variations do not have the same meaning.
[OutputCache(Duration = 0, Location = OutputCacheLocation.Client, VaryByParam = "*")]
create a cache-header like this
Cache-Control: private, max-age=0
Expires: Fri, 03 Jan 2014 12:32:15 GMT
[OutputCache(NoStore = true, Duration = 0, Location="None", VaryByParam = "*")]
creates the following cache-header:
Cache-Control: no-cache, no-store
Pragma: no-cache
Expires: -1
This is basically what you want to see if you want to prevent caching by all means. VaryByParam is optional (at least in MVC5) and the default is “*” anyways, so you can simply use [OutputCache(NoStore = true, Location = OutputCacheLocation.None)] instead.
[OutputCache(NoStore = true, Duration = 0, VaryByParam = "*")]
even creates a public cache control…
Cache-Control: public, no-store, max-age=0
Expires: Fri, 03 Jan 2014 12:36:38 GMT
There is a good post on SO which discusses the difference between max-age=0 and no-cache etc..
At the end all three might prevent caching your data but still have different meanings.