If it's "simultaneously", I go with the PU, but I'm sure they're going to talk about it then and I'm also sure after the game when PU chews out BU a$$ for making his call. Bad mechanics on the part of the BU contribute to this as I'm sure you agree. The only question for BU is how long do I wait before I call foul?

I'm certainly not disagreeing with your thought process. The BU make problems by making a call maybe he shouldn't have. The PU maybe takes too long in trying to signal interference. There is one other factor to consider. Maybe how the play developed, and on one can tell for sure, that the BU had a better view of the batter relative to the batter's box than PU. It's probably one of those plays you HTBT.