I think there are a lot of variables in espresso.
If you temperature surf on the Silvia you should get results equal to that of any hx machine.
If you dont use your hx machine you can get poor espresso too. In addition not all hx machines behave the same either.
It comes down to knowing your coffee and your machine. If you know how to get the best out of a particular coffee and machine then I doubt if you could pick the difference.
Throughput is the main thing hx machines offer and simultaneous steaming and espresso production. If you want to pull a row of espressos from a Silvia over a few minutes you will get a fair variation in temperature of extraction. If you do the same thing on an hx machine, while you can still get some variation depending on the point in the boiler cycle, it will be much less.
The hx machine is in general more stable temperature wise than the Silvia ie. if you pull a shot from a Silvia at the bottom of the boiler cycle the temperature can drop to about 80C during the shot which isnt good. At the top of the boiler cycle it can start at 100C which is too hot. Whether you can pick the difference depends on your palate and experience.
My hx machine if I pull a shot at the bottom of the boiler cycle it might be 90C and at the top maybe 94C. The variability is much less so you dont really need to temperature surf unless you are really very fussy indeed. Commercial machines with 20L boilers are even more stable.
You can also PID machines, the Silvia or HX to reduce the variatons even further.
With espresso you are limited only by your credit card limit!