The AACSB has diluted its brand so much that I would have a hard time seeing it still as a brand of excellence. It was at one time when it was hard to obtain accreditation from the AACSB. It is not so difficult now. Review the list of AACSB-accredited B-schools in the U.S. and you'll find a lot of very mediocre programs with accreditation.
While AACSB may not quite be the standard it once was, it remains the oldest and most widely recognized accrediting body and employers are likely to consider that.
Which begs the question, What other accreditation would you recommend for B school? Is there something better?