I don't know the specifics, but Chrome goes through a great length to sandbox JavaScript, and to isolate one site from the others. That is unique among browsers AFAIK, making it very hard to exploit any vulnerability found in it (which do exist nonetheless). See this question for more info. Chrome is also one of the few that already supports iframe sandboxing, that should help making sites that embed third-party contents a lot safer (though I dunno how often that's used in practice, one well-known example is Facebook apps).
What's notable about NoScript, however, is that is allows you to selectively enable/disable JavaScript and other dynamic contents on a per-domain basis. That is also a unique feature AFAIK, since most browsers either allow you to disable all scripts in a page, or enable all them, no middle-ground supported. This allows you, for instance, to activate only the scripts necessary to access the desired contents, but leave all the rest disabled (in particular the ad scripts from wildly different sources that are usually present in a given page - and which represent a good percentage of the security risks).
That makes it hard to determine "which one is better". My gut feeling is that Chrome is better at protecting your computer, while NoScript is better at protecting the data you enter in the different sites. Since one can't reasonably expect every site out there to have decent XSS protection and to be kept up-to-date with the most recent attack vectors discovered, by minimizing the amount of untrusted code that runs in the same page context (something that Chrome's sandboxing can't do anything about) the chances of private data being leaked from one domain to another is decreased as well.
There are plans to port NoScript to Chrome, which I believe would be ideal, but unfortunatly it's been held back by the lack of support to synchronous access to the page assets by individual extensions. That means one can't inspect a script before it's already executed, making many of NoScript's features unfeasible (and also meaning alternatives such as NotScripts will never achieve a similar level of security).