Great bunch of info there,
I'd add that while turbines do have more power then pistons they actually use that power in working situations. That power margin difference you mentioned is nice for a lightly loaded ship but not for one doing work near mgw.
An 11,ooo pound ship slinging a 9,000 pound load has lots of power but most of it is already in use. You may only have a small percentage of power left to stop you or direct your flight path.
In this case the downwind/ into the wind decision you make will be more critical due to the inertia that you're trying to control.
A rule of thumb for power required I was told a while ago was that a downwind approach/ departure requires 2% additional NG. It may not be exact but it does make you look at the problem prior to becoming involved in it.