OK........
I had a brief chat to my lecturer, and the answer is kind of a combination of what we have both been saying.
He started off by asking me why on earth I would use a compressor through an aux send, but I assured him that all I wanted to know, was the differences on how the two different busses work, regardless of the obvious reason why you would use one in preference to another....
Basically he said, an insert send is not really a send, it is like an output, or a break in the signal path, with a corresponding input before the EQ.
An aux send takes a split of the signal, without breaking the signal path, and depending on the aux master, the aux send could be sending even more than 100% of the original signal.
He also went on to say that if you were using a compressor via an aux send, returning it to a channel would be a better option so you had the choice of EQ'ing the return. Ultimately, you can use the aux send to feed a compressor, but for obvious reasons it is not the standard practice.
I didnt get any technical response, as we were in a lecture, and we try to keep focused on the current subject, but the answer seemed to be yes, you CAN use the aux send to feed a compressor, but you SHOULD be using the insert points.
Apologies to all I doubted! I dont mind admitting I was wrong
Still searching for the technical explanations......One I can think of is that the send is mixed with all of the other sends too, and then through the aux master, as well as back through another amplifier, and EQ etc....so all the while adding noise/distortions of the original sound etc..
But we've been through all that already.....