I was always partial to pet pdt axes x2... Whether you want to or not there will be points in time when you have like 5-6 things at once on your pet if your pull is dirty and/or things wander over and aggro you while you're fighting, so it's never a bad thing when your pet takes less damage.
I don't solo dynamis anymore though, so the only time I ever use bst for anything these days is pet tank scenarios where I just send pet in and keep the f*** back like when I remade my A Shantotto Ascension pants not long ago. Anything that makes your pet "tougher" is always a plus, and even though I don't solo dynamis anymore, I still make use of my pet pdt x2.