Tricky. "However" seems simply contrastive:
1. Burble burble burble. However, blah blah blah.
i.e. you haven't necessarily decided between burble and blah.
But "be that as it may" seems to suggest that while you accept the validity of the burble, you have plumped for blah:
2. Burble burble burble. Be that as it may, blah blah blah.
MrP