Just as good Rob. You then start at a neutral, unloaded position. Ideally you would Jack both sides so that the anti Roll bar has no effect too.Does this article reflect the points you are both making? It talks about the rubber bush working in 'rotational torsion'. And a polyurethane bush working in a quite different way.
http://www.mossmotoring.com/rubber-polyurethane-bushings/
It's certainly been an education for me all this stuff.
@t-tony as most of us don't have a 4-post ramp to tighten the bolts up with the suspension properly loaded, how good a substitute is jacking the suspension up from underneath so it's in similar compression?
Tony.