Fc is best used for comparing text files while comp is better for other content types.

Fc Compares two files and displays the differences between them.

fc \[/a\] \[/b\] \[/c\] \[/l\] \[/lbn\] \[/n\] \[/t\] \[/u\] \[/w\] \[/nnnn\] \[drive1:\]\[path1\]filename1 \[drive2:\]\[path2\]filename2

Parameters:

 /a  Abbreviates the output of an ASCII comparison. Instead of displaying all the lines that are different, fc displays only the first and last line for each set of differences.
 /b  Compares the files in binary mode. Fc compares the two files byte by byte and does not attempt to resynchronize the files after finding a mismatch. This is the default mode for comparing files that have extensions of .EXE, .COM, .SYS, .OBJ, .LIB, or .BIN.
 /c  Ignores the case of letters.
 /l  Compares the files in ASCII mode. Fc compares the two files line by line and attempts to resynchronize the files after finding a mismatch. This is the default mode for comparing files that do not have extensions of .EXE, .COM, .SYS, .OBJ, .LIB, or .BIN.
 /lbn  Sets the number of lines for the internal line buffer. The default length of the line buffer is 100 lines. If the files being compared have more than this number of consecutive differing lines, fc cancels the comparison.
 /n  Displays the line numbers during an ASCII comparison.
 /t  Does not expand tabs to spaces. The default behavior is to treat tabs as spaces, with stops at each eighth character position.
 /u  Compares files as Unicode text files.
 /w  Compresses white space (tabs and spaces) during the comparison. If a line contains many consecutive spaces or tabs, the /w switch treats these characters as a single space. When used with the /w switch, fc ignores (and does not compare) white space at the beginning and end of a line.
 /nnnn  Specifies the number of consecutive lines that must match before fc considers the files to be resynchronized. If the number of matching lines in the files is less than this number, fc displays the matching lines as differences. The default value is 2.
 \[drive1:\]\[path1\]filename1   Specifies the location and name of the first file you want to compare.
 \[drive2:\]\[path2\]filename2   Specifies the location and name of the second file you want to compare.

For more information on both commands, see %SystemRoot%\System32\NTcmds.hlp