Only in Windows, in the latter case, .write('\n') writes one byte with a value of 10. In the former case, it writes two bytes, with the values 13 and 10.
You can prove this to yourself by looking at the resulting file size, and examining the files in a hex editor.
In POSIX-related operating systems (UNIX, SunOS, MacOS, Linux, etc.), there is no difference between 'w' and 'wb'.