Plugins on Master Fader or Main Mixdown Track

[studioslave77]

I usually bounce down my final mix analog and into a 2-track in protools...

I apply compression and a Limiter to give it a mastering..

My question is what is the differnce when applying those mastering pluggins either on that 2 track mixdown track then send the signal to the master fader and do a bounce, compared to putting the pluggins after(not on) the 2 track on the Master Fader track, then mixdown(bounce)?

I hear a difference when moving the pluggins from the 2 track(sounds better i think) than when putting them on the master fader instead. What is the difference,?