The only difference, fo me, is that DB's are easier on my wrist and I seem to get a better stretch. With DB's, I rest them on the side of the chest. With a BB, I rest the bar on the floor. A training partner stands by to make sure the bar doesn't roll away. The straight arm version (DB or BB) also gives benefit to quite a few. Though, to me, the bent arm version gives a better total stretch and more weight can be used. I use both versions, from time to time.
Exceptional exercise with the focus on the lats, pecs, delts,triceps and even the abs. Also affects a increase in the rib box size by stretching the cartilage (between the ribs and the center of the chest). Some gain 2 or 3 inches increase from the rib box alone.. But the trainee must be young enough so that the cartilage does not set as one gets older. Usually the mean average is 23 to 25 before the cartilage sets and becomes harden. Starting while a teenager has a great advantage for a very impressive chest in later years.
The 20 rep breathing squat program alone has been known for a chest/rib box gain in size, due to the forced breathing required. If anyone has done this style program, with serious intent, they will understand what I mean. Some add a lighter set of straight armed pullovers after the squats. To take advantage of the heavy breathing and chest expansion. Good luck.