There are too many variables that can influence the taste of the espresso.
I tend to avoid looking at the extraction process, on the visual appearance of the espresso and taste my espressos blind. This eliminates the biasness from the visual aspect.
Using single origins, blends, dark and light roasts.
Between the E61 and saturated groupheads, I can't detect much differences.
Between the E61 and a Strada(at default setting) , I tend to prefer shots from the strada as the notes appear richer.
Between Strada and a spring piston like the Strega, they are fairly similar.
Between a heat exchanger and a double boiler, yes there's a difference and my preference goes to the heat exchangers.
Base on my preference in tastes, it drew me to simpler machines that cost far less and last longer with lesser problems so why not.
Maybe it's just me but this is the conclusion I had with my partner.