Hands down the largest depower trim is the Ocean Rodeo Freeride bar. It also has the largest potential throw on the market, as you could move the stopper up to 3m up the rigging. http://www.oceanrodeo.com/products/freeride-bar
Most below the bar systems will see a reduced maximum sheet out potential when depowered.
Generally I prefer above the bar depower for myself. I've not noticed a difference in maximum depower length from one above the bar to another.