In defense of the OP, while "identical" may not be possible, you certainly could:
1. Load up your own wavetable in two different WT synths (or same sample in two granular synths)
2. Setup similar tuning, envelope, filter settings across Pigments2 and another WT synth
3. Setup similar modulation on both
4. Use the same number of voices
5. Turn FX off on both
6. Compare the sound
There'd be no "utter nonsense" about using a test like that to compare sound quality. Particularly if you were listening for things like "which filter do I like better" or "can I hear a difference in the wavetable interpolation" or "how does CPU compare between this and Hive2 (for example)?"
I agree that comparing Pad Preset X on Pigments and comparing it to Pad Preset Y on Hive2 is a really poor way to compare two synths, but it's totally possible to do more objective comparisons. In fact, it seems like a perfectly reasonable type of thing to do if one were really worried about spending money a synth they may not need.