Different rectifiers will give give different voltage drops (GZ34 least drop and others the drop increases). This in turn will operate the other tubes(pre / power) at different voltages and therefore different positions on their operating curves. Add to this the fact that everyones mains voltages are also different shows quite how many variables there are. My 250v is very different from others 220v but both are legal here. There are lots's of variables here on how we drive the pre / power tubes long before we even look at makes / types which themselves will also interact with the voltages being given by the rectifiers.
Thanks for your opinion/input, very interesting!