Such questions are difficult to answer. There are too many variables that play into the gun's precision, so if you compared on sample to another and got a concrete answer on which was more accurate, how would you know it was the bull barrel vs the bushing the was THE difference.
The other difference is the ammo. Unless you do exhaustive load development to determine the most accurate load for each pistol, how can you fairly compare the pistols? If you use the same loads, you're comparing the precision of that load in each pistol, not the pistols themselves.
The real question is which one is best for your purpose. I am not sure of all the competitions the Accu-Shadow is legal for at the moment, but I guarantee it's more than the Bull Barrel, so if the Accu is the one that is legal, THAT is your best option.
And if legality in a particular sport is NOT an issue, you get the bull barrel, but it's hands down the coolest Shadow variant on the market.
