Are some of the hand sharpening kits better than others? I've tried the electric and while that's great in the garage, I'm not opposed to doing it by hand when sitting on the cabin porch in the mountains - I have the time!

I looked online and there seem to be more than a couple of options. Do I just head to the local Stihl dealer and buy the one they offer or is there something in particular I should be looking for?