Baking powder is a leavening agent. Baking soda is not by itself, but add cream of tartar and it is -- or if you use a sour product (buttermilk or soured milk).

As for making the cookie softer -- that depends on the recipe and ingredients you have to work with. Several ideas already listed work (extra egg for drop cookies), but it's also good to check the recipe to know if you should sift the flour or not. It may not be a choice of BP vs. BS Hey, if the cookie is too hard, have a cuppa coffee or glass of milk with it. It's the taste that counts!

Years ago i taught cooking to 6th and 7th graders. One girl brought me a cookie to taste because it didn't seem right. One bite and my mouth puckered up like crazy. She had used a quarter of a cup of baking soda instead of a quarter tsp. wooohoooo, will never make that mistake again! Lolololol !

oh sounds like we need a thread with just cookie recipes...

I sometimes use half shortening and half butter. The best of both worlds.

I was a baker in my earlier years & always used half regular sugar & half brown sugar when I made soft cookies.I just used the same amount my recipe called for & used half of each.Also if you want crisper cookies DO NOT use brown sugar.Chocolate chip is really good crisp,Kinda like a bakery cookie.