Well, you always must remember when you are processing a track ITB, you're working with binary code... I mean... After the AD, every processes will be just modifications in the order and long of the code that represents the audio... Somtimes better than others... But they are numbers... 'till your DA do the job transforming again in voltage... so you are in the hands of the algorithm of the plug in compresor that your using.... but any way... they are representations...
If you use a nice hardware compressor, you are processing electricty... and from your mic to your AD, it will be always electricity... the processing of the electricity is more.... Mmmm... Continuous if you want... you're changing values in the voltage... and the components of the circuit add their own characteristics to that voltage... adding that "analog" sound...
If you saw in other way.... if you draw a line with a pen... it's gonna be a line... continuous..... BUT if you use a Sacanner to play with that line in Photoshop, well... looks like a line in the computer... but if you do a zoom in... the line is just a number of pixels.... just littlel squares... you can do a curve with the digital line.... but if you zoom in that line It's gonna be the same squares in other order.... but if you draw a curve with a pen... it's gonna be continuous...
After all this boring Speech
.... You can use plug ins or hardware... but remember... the plug ins are "representations" of what happen in the analog world... The plug ins are really usefull when you can't buy 100 compressors... and you need them... you can put 100 Comps in your daw... But the Hardware alway will be "the real thing"...
Probably you're gonna get more pleasant results with hardware.... after all it's not a representation...
My 2 cents...
Cheers!