On Wed, 30 Sep 2009 12:50:50 +0100, Stephen
wrote:

As I understand it there
are two types: one that has rotating blades, like a large food
processor. The pros are that it will cut leaves into a fine mulch but
the cons are that they are noisy, the blades quickly blunt, and they
don't like thick branches.

They are hideously noisy, jam frequently and tend not to last well.

I understand there is a third model made by Bosch that uses a helical
blade. How does that compare? What are its pros and cons? Would that
work in my situation?

Having had two rotating blade and one Bosch it is no competition. The
Bosch is quiet, rarely jams, eats quite large branches and chops up
leaves a bit - certainly sufficiently so they take up very little
room. Vastly better than the high speed things.