Although very similar sounding in some regards (especially secondary and tertiary signatures) they are actually quite distinct from one another in their tuning approaches.
NiceHCK EBX21 are indeed an interesting one... although very "
bright" leaning in many aspects their primary signature (red shaded oval) actually sits near to (on) the "
flat" neutral horizontal line (axis). From there they tend to reach out with a "
detailed" and "
critical" prominent secondary characteristic (blue shaded balloon) and come across as being very analytical & clinical (cold-sounding). With a weak tertiary characteristic (green shaded arrow) they do have a minor tendency to sharply shoot out towards "
hard-harsh" upper mids; sometimes sounding very forward and aggressive. Some people believe the EBX21 have a "balanced" tuning but their rather strong lean towards upper mids and treble, less emphasized bass, and strong analytical nature have me argue that they are not... nonetheless, I have indicated this possible additional tertiary sound signature (purple shaded arrow). The EBX21 are truly excellent reference earbuds for critical listening... that is if you can handle their bright cold analytical nature. I really liked these earbuds but sadly it was way too fatiguing for me giving me atrocious head and ear aches.
Rose Technics Maria I & II are truly amazing earbuds with one of the widest (if not the widest) and most open sound(head)stages currently available (only competitor in this regards is probably the
Toneking (MusicMaker MrZ Tiankui) Dendroaspis Viridis). The Maria I, and especially the II, primary signature (red shaded oval) is far more "
mid-forward", "
mid-centric", and less "
bright" leaning in nature than the EBX21 which is more flat and neutral in it's presentation. The Maria I & II show a weak secondary signature (blue shaded balloon) that reaches out to "
hard-harsh" upper mids that can come across forward and aggressive. A sometimes prominent and opposing tertiary signature (green shaded arrow) exhibited by Maria I & II is a tendency to reach out towards the "
hard-harsh" lower treble area with certain recordings and genres. Again, very fatiguing for treble sensitive folks such as myself but if you can handle that these are definitely end-game god-tier earbuds worthy of serious consideration. Special Note: although available in two different sizes, due to their unique shell design 'the fit' can be a big issue for some people.