Generally 209s are louder and generally less expensive. With .22s you can get any number of loads from soft acorns to heavily loaded blanks. You can get .22 loads at any store that carries .22 nailers like Fleet Farm, Menards, Lowes, Home Depot. Also .22 blanks are available from many sporting goods stores like Gander Mountain, Cabela's, etc.
Also check this old thread: viewtopic.php?f=69&t=23705&p=214614&hilit=blank+pistol#p214614