Cool. 43 views and no replies. Well, now we have a rough idea about how many people come to this forum and check things out every few days.
Actually, we don't really know at all. A lot of the accessions will be search bots, and the rest may well just be the results of seaches by non-members, who when they find nothing more than a question, go away again.
No rellies? Well, nobody's
obliged to - especially when to some people it might seem like stating the blindingly obvious...
The result is either going to be absolutely the same, or impossible to predict. If you manage manually to implement the same compression envelope that an automated system does, then the result
will be the same. Since you can't possibly achieve this though, then the result is going to be different. How different it is depends
entirely upon how you draw the envelopes vs the machine. It will apply an algorithm consistently, but you won't be able to match this manually at all, because you can't measure what the system measures in able to do this.
The next bit isn't quite so obvious at all, and may be more like the answer to the question that perhaps you
should have asked - is one approach generally better than the other? But once again, there isn't an absolutely clear-cut answer. People like broadcasters often 'ride' the levels on performances, but generally they do this to restrict the dynamic range (aka not over
or undermodulating the transmitter), which isn't the same thing as catching the peaks at all, and the result sounds somewhat different. But, if you have a vocalist who uses a dynamic range that's too great for a mix, and also you have short peaks in the output, the chances are that the best approach will be to use both methods in a complimentary manner. So you might catch the worst peaks with the compressor set so that it doesn't attenuate them too much, and then ride the overall level with an envelope control, which is not anything like as good for controlling short peaks anyway.
What you will have achieved at that point is the manual equivalent of an AGC system - the bane of our lives! But because you've done it manually, and effectively in a predictive way, you won't suffer from all of the recovery problems of a 'normal' AGC system, and the result will sound far better.
Ultimately, you need to fix the vocal so that it sounds correct within the context of the track at any given point - and how much you need to alter it depends entirely on how good the singer was when recording it. And that is such a moveable feast that it's impossible to generalise on a method that's going to work every time, because sometimes you need to do nearly nothing, and on other occasions it's major surgery that's required to make it fit. And it's not just compression that you need to use to do this either - quite often you can make a significant difference by EQ'ing the voice as well, or instead. But nevertheless, the ultimate goal is to make it sound like a natural performance, and as though you've done nothing to it at all - not always such an easy thing to achieve, which is why it's not possible to be prescriptive about the method in any given instance.