I use both. There are some things you just can't (at least I can't) do with one or the other alone. Stuff like relieving the background, blocking out the bird etc. I use the high speed. For detail work I make little chisels and knives out of cheap "needle files" and hone them on a leather wheel. High speed for me on really tiny detailed stuff just means I can screw it up, only faster :) so I use "knives".