B at teh end typically is for AnnexB (nor rev,.B)., The second modem version is v2.
The problem about DSL connection most of time are out of the modem.

well....obviously 8970B is different from 8970.
If your ISP provides Annex B,then you need to buy 8970B(only several countries use Annex B)
and if your ISP provides Annex A,then 8970 is what you need
if you buy a wrong one,just replace it with what you need in the shop where you buy 8970 or 8970B