lets not exaggerate , i guess you hear the blm-3 in your life , really not in the same league :-)
by the way , you can do the dpas tricks with every lavalier , we do it all the time placing lavalieres on car visors to get dialog from actors .
what really matter on pzm mounting is the surface which has to work for the mic , at least 2-3 sq feet of reflection.
if it only conversation in the class room i dont see any benefit waist money on dpa - the at would sound the same .
i also like to place these for a drum kit from the distance , working quit nice by opening the sound .