fileread is very basic. It will often not work for files that are encoded with UTF-8 and can only handle plain text files. That is why my readfile function isn't just function str=readfile(fn),str=cellstr(fileread(fn));end, although for simple files it will probably be mostly equivalent.
extractFileText on the other hand has much more options. This makes the function very versatile (as you can use it on pdf, doc, etc), but that means it has to check everything as well. It will also probably handle different encodings better. Everything that makes a function more versatile will require more time.