Both are iso e super bombs--which is fine with me, I like the molecule.
Terre d'hermes is in my opinion the better scent, and it is the scent that got me interested in fragrances. It will always be special for me, it was my signature scent for two years. Unfortunately I hear it has been reformulated... so its greatness has in all likelihood been irrevocably diminished.
I do like Grey Vetiver. It has this enveloping feel at the top, but the drydown is rather ordinary. I don't even think of it really as a vetiver scent, to be honest, since it feels so clean. I agree that it is a great work scent--and I would say it is not just "inoffensive" but rather classy for a work scent.
If I had to choose between the two, I would pick TdH (vintage) any day of the week. But now that it appears that TdH has been weakened, it might be the case that Grey Vetiver has the advantage over the reformulation.