I have finally found time to check what the difference is between the
155 CD and the 160 CD editions - that is apart from different
performers on a few discs.
The 160 CD box includes the St Luke Passion BWV 246 and the St Mark
Passion BWV 247 - 2 CDs each, which are not included in the 155 CD
box, and the Christmas Oratorio is on 3 discs rather than 2. So that
explains the 5 disc difference.