Like Rich I do a little of both.
But it depends on what I am doing also.
In trying to do a version of an original rifle the placement of the lock can have an effect of the appearance of the wrist. A rifle that has the fence right the end of the barrel will look different if the lock is placed forward to clear the breech plug.
Some original rifles have very short pulls, between 12 and 13" lengthening the pull will require careful work to avoid getting the rifle out of perspective.
Heavier/lighter barrels will require modifications. Some originals have barrels that are heavier at the breech than the typical barrel found today. This will change the look.
This is why its important to draw in your parts on the blank during layout. Locating the lock locates the trigger etc etc.
When sawing out remember that the surface will require wood removal to smooth the saw cuts, so the ".600" in the photo, to be removed prior the cutting the barrel channel in the photo allows for this.
Its also important to know that some photos of rifles are distorted due to the lens used or camera angles.
Dan