Ah, I peeked into the two files:
"AmigaOS ROM UPDATE" is version 44.26 and contains:
console.device, v44.6
ram-handler, v44.21
scsi.device, v43.35
filesystem.resource, v45.7
filesystem, v45.9
"AmigaOS ROM UPDATE.BB39-2" is version 44.57.
All the modules inside are newer versions,
console.device, v44.8
ram-handler, v44.23
scsi.device, v43.43
filesystem.resource, v45.10
filesystem, v45.13
and it contains these additional modules:
shell, v45.7
exec.library, version unknown
bootmenu, version unknown
The exec.library in the BB2 update locks up my system. However I can use the ROM update if I exclude that module.