The acids and bases in the milk help to break down and tenderize the meat as well as pull blood out of the meat. Salt water pulls blood (and brakes up blood clots) out, as well as pull salt into the meat through osmosis. Both procedure work well (and you could do both) but saying which one is better is a matter of opinion. Similar to saying if salty food is better or worse than sweat food. so, in the end it only maters what your wife prefers
The things that you should not overlook are surface area, and time. The more surface area you have the more (and faster) the procedure will work. Also the length of time you soak your meat affects how well it works. With either method you have to change the solution every other day at worst. When the water content in the duck match the content out of the duck the procedure stops working.
I would recommend no less than 1 week for ether of the two. I would also recommend cutting your meat to the size you want before you bleed it. But the most important thing of all is to get rid of the silvery membrane on the meat. You may also want to consider how you like your meat done. If you like it rare poppers will do. But if you don’t want it to quack when you bite into it you may want to consider chili or stew. As far as making a difference, if either is done well, it is the difference between night and day.
Salad... it's what food eats.