Well, and who exactly said the temperature during the shot must be flat? Does really the flat temperature profile make a tastier shot than HX humped temperature profile?
Yes, the PID makes the strike temperature much more repeatable but - it takes a while until the boiler and all the water inside settles on some stable temperature after the "shock" caused by last cold water intake & reheating it again. With HX you can make almost infinite number shots one after another with almost minimal delay between; OK, never tried that with Oscar but I really think the machine will be nearly as able as Promac Club ME which I have used even on quite busy occasions without any problems.
I personally think the HX is much more versatile and able than SBDU machine. And getting used to observing the cooling flushes can't take you more than a month. When you nail the technique, HX beats the SBDU even if you really want a flat temperature profile (not mentioning you can make almost any temp. profile you want just by carefully tuning your operation routine and pstat setting with HX machine).