Adjusting audio waveform volume Vs channel volume

Hi was just wondering what advantage or disadvantage is associated with changing the volume of audio waveforms via the draw tool in the arrange window as opposed to automating channel volume?

I have recently discovered the draw tool method and like it because it seems to be quicker and easier to make detailed changes but i wondered if there was a disadvantage to doing it this way?

-Look at the signal flow that would be the first difference.
-Try to draw a +6 dB gain with event envelopes.