What makes it "new" is the transfer bar mechanism which allows you to safely carry the gun with a round in all six chambers. On the old "three screw" models, if you left the hammer down with a round in the cylinder and dropped the gun just right, it could accidentally fire the round which is why you will see people suggest that you load one, skip one then load four and keep the hammer down on the empty cylinder.
Unless you already have a 9mm pistol with a lot of spare ammo laying around, I would save some money and get the straight .357 version - which is what I did when faced with the same decision. You can still shoot 38 Special and .357 Magnums from the same cylinder with no issues.
A month or two ago, CDNN Sports had 50th Anniversary Blackhawks for about $359. I doubt however they have any left at that price! Even so, a new .357 only is selling for $403 at Buds. Heck of a deal!
Scott