well in the defense of the duraforce 2 stroke, they were jetted too small (emission standards) making them bog like crazy in thick grass because they run too lean. The F series lawnboys have an air adjustment on them and they will dust a 4 stroke when adjusted properly. Nothing but a two stroke lawn boy will be touching my lawn. If you ever get a chance to jump on an f series lawn boy do it because you will not want to mow with anything else after using it!
The solution with the reason
Great
I too am a two stroke fan, being lighter, there is no reason for self-propelled, at least on level grounds.
Also, they are less noisy.
Now, I too own a 10685, an excellent unit, but it could be better.
A smooth plastic deck(Honda) to allow for better mulching...Around here, the grass is always wet, this leads to accumulated mud and grass under the deck - quite the problem..
I really do have a lousy lawn, I must admit...