BAG an M&M are very different works, not entirely complementary.
BAG is very good indeed as a one-volume thesaurus, but the articles are not
always written with the same lexicographic finesse, and the apparatus with
testimonies outside the NT must be used cautiously: many times it gives
very good parallels indeed (far better than LS&J), but sometimes the
references look like a mere juxtaposition of testimonies of a word without
consideration of its Greek meaning and use, or there is no way to know why
this reference is there, and not another.
On the other hand, the lexicographic analysis of M&M is almost
always excellent, and the extension of the papyrological material quite
good, if we consider the date (for 25$ it's a gift). Nowadays you must use
in addition to M&M the papyrological lexica (mainly Preisigke's) and the
Berichtigungsliste; for the epigraphic testimonies, you must go to the
indexes of the collections, the An'ee Epigraphique, the PHI #CD-ROM, etc.
For words before diw/nuxos, you must look up the DGE
BTW, there is a large "Diccionario Griego-Espaņol del Nuevo
Testamento" in preparation (without any relation whatsoever with the
"Diccionario Griego Espan^ol", DGE) which is a large undertaking. A book
explaining its metodologies appeared last year. I'll let you know as soon
as this DGE-NT appears.
___________________________________________________________________
Daniel Rian~o Rufilanchas
c. Santa Engracia 52, 7 dcha.
28010-Madrid, Espan~a