1. From the Advanced Programming in Unix Environment :

…

The difference between getc and fgetc is that getc can be
implemented as a macro, whereas fgetc cannot be implemented as a macro.
This means three things:

• The argument to getc should not be an expression with side effects.

• Since fgetc is guaranteed to be a function, we can take its address.
  This allows us to pass the address of fgetc as an argument to another
  function.

• Calls to fgetc probably take longer than calls to getc , as it
  usually takes more time to call a function.

…

2.

Seems like the differences are, in 99.9% of the cases, meaningless.

One point which may make a difference - The man page says getc() may be implemented as a macro which evaluates stream more than once .

It could lead to strange behavior in some (not very useful) cases, e.g.:

FILE *my_files[10] = {...}, *f=&my_files[0];
for (i=0; i<10; i++) {
    int c = getc(f++);    // Parameter to getc has side effects!
}

If getc evaluates f++ more than once, it will advance f more than
once per iteration. In comparison, fgetc is safe in such situations.

http://stackoverflow.com/questions/18480982/getc-vs-fgetc-what-are-the-
major-differences