They're pretty close to the same.
There are differences though in the way you can train with
board presses that you can't do off pins. With boards you can let the weight slam into the board and get a rebound effect (not quite like pins would give). That could help simulate using rebound of a
bench shirt in a competition (technique).
ALso with board presses, some people touch the board, some people let weight sit on the board, some people let weight sit on the board while it rocks and then throw it back (pitch and catch type).
The point is the same really though, to work on weakpoints.