My first choice is neither, but rather the K&R standard:
The C Programming Language (book - Wikipedia, the free encyclopedia). It really is the best book. One of the books' authors designed the language while the other designed the AWK language.
While I like O'Reilly books, these are generally targeted toward a slightly more sophisticated audience. Reader reviews from Amazon confirm that this book's best features are its detailed reference of the standard library, an absolute necessity if you are going to be programming in a non-Windows environment; the book also contains explanations of using gdb and make, rather necessary tools for modern C development in UNIX. By contrast, the reviews about the Sams book indicate that at 900+ pages, this book is geared toward even the beginning programmer, and is described as teaching a "Plain Vanilla" C, ie, not especially for UNIX nor Windows.