I believe that you can specify which of the disasters you want it to go for but the fact that they use the money for general operations didn’t matter a BIT to me when they were here helping in the aftermath of Katrina. When you need them they are there and that meant a lot to a lot of us.
I agree, though, that the Salvation Army is the best of the best. I just found this to be very easy and convenient.
I would always trust any group you personally know about...ie: your church....