Think the important metric regarding HiRes/ERES and other modes of enhancement, however they are implemented, is the ENOB after the mode is invoked which takes into account all the degrading/limiting factors, wether in the analog channel, ADC, or post processing numerical limits.
Things like input referred noise level and complete end to end channel linearity become issues that differentiate various systems within a given bandwidth. Various techniques are available to study such, one we often use/prefer is the classic Two Tone IMD method.
Another important factor, often overlooked, is the channel overload recovery. Where one is "looking" at a tiny signal just after a much larger part of signal that can saturate the channel. This can cause lots of issues with resolution enhancement techniques, since these may employ some form of waveform averaging. Here is where a true higher resolution ADC shines as you can "see" the tiny signal detail with the higher resolution ADC and remain still within the channel limits without resorting to post ADC resolution enhancement techniques. Of course assuming the channel noise level is low enough to allow one to "see" the tiny waveform details, which implies a basic good fundamental ENOB for the channel and ADC without resorting to enhancement techniques.
Anyway, lots of interesting metrics for these new DSOs , which in reality are really Impressive Data Acquisition Systems disguised as simply a Scope

Best,