You took two MP3 files and did an ABX of them. That isn't useful, it just tells you that you can hear a difference between the two MP3 files, but you don't care about that.
You said you were trying to figure out which settings are better for that one specific sample. Is that still the case? Then you need to do the test suggested here:
I suggest doing them in order too, since if the first fails the second will fail too.