[EDI-L] Benefits of a TA1 over 997?

[need2know711]

Hello all.  We recently had a Trading partner start sending us ISA with a TA1 
request.  Anyone know of the benefit of a TA1 over a 997?  Every once in a blue 
moon I will have a TP send a 997 requesting this , and I just ask them to turn 
it off.  I don't have experience with the TA1, but from my research I can't see 
the benefit over the 997 other than if there is some issue with the envelopes 
(which is exactly a good reason to use them).