Na mimi ntaanza kuweka amira aisee
Kuna mwingine alikuwa na wasiwasi kama wako juu ya kutumia amira na hapa chini ni majibu;
Baking powder, especially if too great a quantity is used, adds an unpleasant flavor to a baked good. Even in an appropriate quantity it can be noticeable and it certainly doesn't do anything to enhance the flavor. Many baked goods traditionally don't use a chemical leavener at all, but instead rely on technique. Creaming butter and sugar together or whipping egg whites was historically used to make cakes which rose solely based on the bubble network that was created.
Yeast, on the other hand, creates a delightful flavor that you associate with your favorite crusty loaf of bread. Yeast can be used not only in making bread but also in some excellent cakes (St. Louis Gooey Butter Cake, for example, although many "knock off" recipes cheat here and miss out on the true goodness). Yeast also provides a significantly different texture during the rising due to the intentional creation of a gluten network (usually something you absolutely don't want in a quick bread or quick cake) - you don't get a crumb with big, airy wholes from baking powder or baking soda with an acid.
Also, in my experience baking powder lasts six months in the pantry and yeast lasts at least six months in the fridge. The shelf life is not so different.
If yeast scares you, you may want to check out some of the proponents of the no-knead bread technique.
For a lot more information on this subject, there is a recent publication that covers all sorts of leavening agents.
First of all- yeast is not nearly as complicated to use as your question would seem to imply. Yes it is a living organism but it is a very simple one. Active dry yeast will stay viable for years in the freezer and it is easy enough to avoid adding it to water that is too hot for it.
It can be inconvenient to wait for yeast products to rise but there are two very important benefits:
1) Yeast will keep producing CO2 as long as there are sugars to eat- this means that you can raise tougher doughs- like bread dough- where baking powder just wouldn't have enough lift.
2) Flavor. This is the big one. Baking powder tastes gross. At best you can't taste it at all. Yeast risen products have a distinct complex flavor that you can't get any other way.