I used to donate calls to all of them, NWTF, DU and Delta. For a few years I would receive a nice thank you note. Slowly the thank you notes stopped, and I kept donating. Then I found out some of the donations were not being given as prizes, but being donated to visitors. I complained to deaf ears. So I quit making donations, if I had wanted to donate to someone in a national headquarters I would have sent them one.
As to the donations, for a few years I would get the receipt saying I donated X amount in calls for prizes. All well and good, but when you donate items you make you get the lessor or, the value or your cost in the call donated. A call that costs you $10 to make and sells for $100 is only a $10 deduction. With them giving my calls to visitors, I received more benefit by joining the organization than I received from donating to them.
Now, I am no longer a member or donate anything. Instead I donate to various local charity auctions and other local functions, at least this way I know they are staying local.
Marvin