IMO the more keywords a UA contains, the better (with some length limits). More words allow crisper honing on multiple conditions (IP & UA) to lessen the innocents ;)
I'm not aware of a list published which provides insight into what should be present per an operating system, although one may exist.
The most common OS-UA restrictions are based upon the versions of MSIE and their compatibility with either "Windows NT" or another MS OS.
Firefox generally contains clean and short UA's.
The latest Chrome UA's are fairly consistent, however there may be some variation for OS.
Linux, Android and a few other OS are certainly easy to focus upon.
The mobile devices (per your Samsung example) number in the thousands.
Not much help in the way of what you were looking for.