>Can someone give me a clear answer. When is it more appropriate to use
>Begin Transaction .... End Transaction vs Bufferring .. TableUpdate

Table buffering will only take care of individual tables one at a time
Transactions OTOH locks the records it processes

combining both you can implement a two-phase commit
Do a tableupdate for all the related tables inside a transaction and if one fails you can ROLLOVER the whole transaction

Arnon