Same code different characters Note: This challenge only allows answers in compiled languages

Task

Your task is pretty simple, make two different programs that when compiled result in the same output.

Scoring

Here is where the fun comes in.  Your score will be the number of unique bytes present in exactly one program.  For example if your two programs (encoded in IBM Code page 437) are

☻☻Program A


and 

☺Program B


The characters that are in exactly one program are

☻☺AB


Thus the score is 4.  Note that ☻ appears twice in the first program but is only counted once.

Your goal is to get the highest score, the highest score possible is 256.

Here is a scoring program that works for ASCII encoded programs.

Stipulations


Every byte in both programs should be able to be replaced with a different byte causing either the program to compile into a different result or fail to compile all together.  Removing any byte should do the same.
You may use any compilation flags as long as both programs are run with the same flags.
The resulting compilation should be static (i.e. should not vary from run to run), if results vary from machine to machine indicate the machine it is intended to run on.
The output of compilation should be byte for byte identical not "equivalent" or "similar enough".
The output of the compilation should be non-empty
Warnings/Errors need not be the same between compilations
If either the programs or the compilation include unprintable characters be sure to include a hexdump.  Although it is not technically required.
Perl, score 254 + 2 = 256

Here's a hex dump of one program:

00000000: 6c65 6e67 7468 2700 0102 0304 0506 0708  length'.........
00000010: 090a 0b0c 0d0e 0f10 1112 1314 1516 1718  ................
00000020: 191a 1b1c 1d1e 1f20 2123 2425 2628 292a  ....... !#$%&amp;()*
00000030: 2b2c 2d2e 2f30 3132 3334 3536 3738 393a  +,-./0123456789:
00000040: 3b3c 3d3e 3f40 4142 4344 4546 4748 494a  ;&lt;=&gt;?@ABCDEFGHIJ
00000050: 4b4c 4d4e 4f50 5152 5354 5556 5758 595a  KLMNOPQRSTUVWXYZ
00000060: 5b5d 5e5f 6061 6263 6465 6667 6869 6a6b  []^_`abcdefghijk
00000070: 6c6d 6e6f 7071 7273 7475 7677 7879 7a7b  lmnopqrstuvwxyz{
00000080: 7c7d 7e7f 8081 8283 8485 8687 8889 8a8b  |}~.............
00000090: 8c8d 8e8f 9091 9293 9495 9697 9899 9a9b  ................
000000a0: 9c9d 9e9f a0a1 a2a3 a4a5 a6a7 a8a9 aaab  ................
000000b0: acad aeaf b0b1 b2b3 b4b5 b6b7 b8b9 babb  ................
000000c0: bcbd bebf c0c1 c2c3 c4c5 c6c7 c8c9 cacb  ................
000000d0: cccd cecf d0d1 d2d3 d4d5 d6d7 d8d9 dadb  ................
000000e0: dcdd dedf e0e1 e2e3 e4e5 e6e7 e8e9 eaeb  ................
000000f0: eced eeef f0f1 f2f3 f4f5 f6f7 f8f9 fafb  ................
00000100: fcfd feff 273d 3d32 3533 6f72 2078 2829  ....'==253or x()


and here's the other program:

"\\"


Perl isn't normally thought of a compiled language, but it is; it's first compiled to bytecode, and then the bytecode is executed. You can apply a filter on the bytecode (e.g. to dump it rather than running the program) using the -MO option. Both these programs compile into the following bytecode (disassembled using -MO=Terse):

LISTOP (0x564fcd99f020) leave [1] 
    OP (0x564fcd99f148) enter 
    COP (0x564fcd99f068) nextstate 
    OP (0x564fcd99f100) null [5] 


Explanation

Perl replaces all statements with no effect (such as string literals on their own) with a hardcoded "statement with no effect" statement in the resulting bytecode, so both programs compile to the same thing. In terms of character replacements, replacing most of the characters from program 1 with apostrophes will cause it to fail to compile (or replacing the apostrophes with 0). In program 2, replacing the any character with c will cause the program to fail to compile (as \c takes an argument).

As for character deletions, the first version of this answer predated the "radiation hardening rule" (that deleting any character must change the behaviour of the program). This updated, radiation-hardened version works via the use of a checksum; if deleting a character doesn't outright cause a syntax error, the code will compile into a call to the nonexistent function x. The Perl compiler doesn't optimize out the call in the case where it's made (and in general doesn't seem aware that the function doesn't exist), and thus the output is different. However, Perl's constant folder is capable of seeing that the un-mutated program is a single statement with no effect, and thus optimizes the whole thing down into a single statement like before.

I originally misread the question as counting only unique characters from one program, and tried to optimize for that. Clearly, program 2 needs to contain at least one character in order to generate the "statement with no effect" opcode, meaning that the best possible score in one program is 255. I haven't yet found a way to include a backslash in program 1 in such a way that the character immediately following it can't be replaced in such a way as to cause the program to break, but it wouldn't surprise me if it were possible (leading to a score of 255 + 1 = 256).