Their website has a good differentiation between the families.
http://www.brymen.com/Products2.htmlThe highlights:
BM78x is the newest.
BM86x has the crown for the most sophistication and features, although it loses in some features to the BM78x (autohold, for example).
BM85x is the series that came before BM86x and was the previous top of the line.
BM52x/BM81x/82x/83x tends to be a bit mumbled as price/features are very close to call. BM52x has datalogging.
BM25x are the smaller meters with decent features such as bargraph, Loz, etc. BM257 is quite featured for the price and it also has datalogging.
BM23x are the smaller meters with less features than BM25x, however, Dave's blue meter is a BM235 and it is also a notch below the BM257 and quite featured.
Simple, no?
