As with everything there are good and bad implementations. My Glockenklang Blue Rock, for example, sounds bloody amazing even at war volume. No loss of “heft”, no thinness to the tone. It’s in the execution of the preamp and power stage.
Think back to the early Ashdown examples - the Little Giants I think? They suffered from a weak preamp. Ashdown fixed that with the MiBass series then moved on even further with the RM series.
The other thing to remember is the power amp class (A/B, D etc) is only part of the story. It’s the power supply where a lot of the magic can happen as that’s what needs to deliver to allow the power amp section to do its thing. The SMPS designs in many class D heads work differently from the traditional toroidal transformers etc but again, it’s in the design and implementation. Trace Elliot apparently used to use the big PSUs even for the lower rated amplifiers, which is one of the reasons those lower rated units could continue to deliver clean lower as they had headroom in the supply rails. Then you have the previously-mentioned Class A/B Markbass LM heads; they will have an SMPS for their power supply otherwise they wouldn’t fit in that box size - but clearly it’s been designed to work well
The newer generation ICE modules definitely felt to me to be a better design than the earlier ones, but my Glock uses something else entirely (I can’t remember what!) which is slammingly good.