Hi
I don't have experience with A.Bullfrogs, but as large anurans and hunters of live prey movement I would suggest keeping them separate as a good practice.

I can only see advantages to that; if they defecate at same time in the water dish you will have twice the crapp in the water than it will be bad very quick, when they go for food even if the one is given with forceps they can try both at the same time and get hurt Involuntary .(any injury could be a start for a infection) they could like the same spot to borrow and together one will have to choose another place.
I think they will more comfortable and with less stress even more happy if you could give them separate homes with equal quality (separate heating sources, different water dish, different targets that can be watch and hunt without competition)
I always think that different enclosures are backups, if something goes wrong you can still have a copy