he may be the best in your opinion,but this bring us to a point raised before ,subjective opinion.
now there is no denying he[robert harbron] is a very good player,I certainly prefer him to some of the others mentioned,whose playing[ im0] are reminsecent of typewriters, but that he or anyone is the best is just an over simplification, there is no best, music is not like sport, music is a very individualisitic genre.
when i listen to nic jones or martin carthy, i enjoy them both, i dont have to make immature judgements that this one is better than the other, they are different, but both very good.
likewise there are many good concertina players,all of whom are different[thank god for that], and whose differences in style provide and maintain interest.
to say Robert Harbron is better than Alistair Anderson or Steve Turner is rather like saying an orange is better than an apple or a banana.
finally to lump all 3 concertina systems together is just silly., it is akin to comparing a c melody sax with an alto sax or a soprano sax.
the[EC, ANGLO, DUET are three totally different instrument] all with different advantages and disadvantages