Well, people will argue this, but its effects. If you master effects, you can be creative. Unless you make your own brushes, your not being creative at all, seeing how someone has used every brushset made that is public. Effects can differ, and most of them people underestimate, like the blur tools. Well, thats my opinon.
Depends really if someone has the time to master effects if not they prefer brushing because you can still be creative with them and get totally different outcomes everytime like effects
for grunge most people will say brushing, there is no better way. I mostly brush myself but I did filter alot at one time
brushing most of the time sometimes some filters/effects. really depends on the type of mood and sig im working on.