Well, an article in
Allure said brow powders are too hard for average users, but that's what i've been using for quite a while. Previously i was using a fairly standard brow pencil (not the new MAC Veluxe Pearl brow pencils) and they give me a thick smudgy line even when they're sharp.
But i have naturally
very thin brows, sadly now with some bare spots - i guess my brows are going bald with old age

So powders are much better and give a softer look than pencils - i apply with a fairly standard angled (brow / eye) brush. And the (Dirty Blond) brow gel cream is much more controlled - i use a very fine pointed, slightly stiff, artist's brush, which is like a very fine eye liner brush.
I got one of Anastasia's brow gels - with a spoolie in the tube - and while the color is good, i just don't have enough brow - in terms of shape and the number of hairs - to make it work with the spoolie. I should experiment using a brush, since i like the golden taupe color.
Ultimately, I think what works best really varies with what look we each like for ourselves + our makeup skillz. I don't like dark heavy brows on me, so
i use brow colors that are a little lighter than my hair.