Would you back your claim with what you consider to be decent loudspeaker ? Then we can calculate how much will the sound level drop at say 3m (or god forbid more) distance and possibly find some distortion mesaurements at different levels just to see if your claim stands strong.
Look up any loudspeaker with 123dB peaks. Say a JBL M2 if I recall correctly.
Now take something that has half the perceived max volume, like a Genelec 8260 which off the top of my head is around 113dB peaks.
Let's play some music at 80dB average, and see what happens with a peak 15-20dB above average.
What would the measurement look like? My money is on them playing about 100dB each. So in effect, one has a dynamic range of 20, and the other has a dynamic range of 20dB.
Until you push the 113dB speaker so that it's hitting its limits, both speakers are equally 'dynamic' in that neither is acting as a dynamic range compressor or expander, the latter of which people like to pretend dynamic speakers do.
If you're talking about higher SPL without compression, great. That's called "speaker A louder." not, "speaker A sounds more dynamic than speaker B."
If someone likes loudness that's fine, but that's not dynamics and isn't going to be a notable difference between two speakers operating well within their respective capabilities.
Even if a speaker can do 200dB, it is not inherently more dynamic... And likely the person isn't using the word dynamic to mean dynamics.
An accurate observation would be something like "speaker A could go louder and speaker B was being pushed so there was clipping and compression and it couldn't handle the dynamics."
If no consideration of the situation or context is given then yeah: Blast everything and whatever can go louder 'sounds more dynamic' and car audio is where it's at.