The only mixing bowl I have for now is a plastic one. But recently it came to my mind that I should have bought a stainless one instead. Is there any pros of plastic bowls, or some task that's best done with plastic bowls?
For your average mixing task, pretty much any bowl (of the right size, shape) will do. Also, "plastic" isn't one material, it's a bunch of different materials. For example, some advantages of polypropylene bowls do not apply to melamine formaldehyde bowls, but both are plastic.
So, here are some advantages of a polypropylene (PP) bowl over a metal bowl:
Of course, they have disadvantages too:
And there are things which are just different, like metal conducts heat better (so it works better when cooling in an ice bath, but also you're much more likely to get burnt on it), metal is denser (PP floats, metal doesn't).
If you get metal bowls, except for a few applications where copper is nice (those egg whites, again), you want stainless steel. Stainless is fairly resistant to acid and also corrosion (plain steel is not). Note that stainless comes in different grades, which vary in their corrosion, rust, and acid resistance.
There isn't much difference at all really. I have ceramic bowls, glass bowls, steel bowls and plastic bowls. I use my plastic bowl the most as its lighter and has a 'grip' on the bottom. Steel mixing bowls are heavy and if you use an electric beater make a really loud noise as they strike the bowl. No nonstick steel or plastic bowls exist on the market (as far as I'm aware of) however ceramic ones do. Metal bowls are supposedly easier to clean than plastic bowls as plastic bowls tend to cling to fats and lipids more than metal bowls however I have only seen this referenced (albeit frequently) in meringue recipes where it really matters. Weighing up the odds, I don't think it's worth it to go out and buy a steel bowl if you've already got one as the difference is to minimal.