I'm coming into the discussion a little late, and I'm not sure if I have any fu, except maybe fubar, but here goes...
Even though some of the discussions of guitars made my eyes glaze over
I get the point. The quality of espresso isn't solely dependent on one factor. Changes in any of the various influencing factors can impact the result. So... Given consistency in coffee (yeah, that;s not always true), the grinder and the barista, an improvement in the machine
should produce an improvement in the end product. I'm not knowledgeable enough in the intricacies of espresso machines to back that up technically, but I can show the effect of the machine anecdotally.
When I purchased my Alex I had my Millennium laying around for a couple of weeks. When the gentleman who ended up buying the Millennium was here looking at it I had it fired up and we were pulling shots so he could get a feel for the machine. He asked if he could try a shot from the Alex, which was also fired up, so we tried some and we both noticed the difference in the shots from the Alex. The beans, grinder and barista were the same, just the machine differed and the shots from the Alex were noticeably better. They had a more complex flavor profile and better mouthfeel.