All I really know about long keels is from what people have said. They tend to track well and don't tend to make as much leeway, but perhaps at the expense of speed due to the wetted area, and they are hard to steer backwards. Not being particularly manouverable forwards isn't really an issue if you're spending several hours going mostly in a straight line.
Modern flat boats (like the 2017 Dufour I learned on) are highly manouverable at slow speed, we practiced spinning the boat on the spot by using prop wash over the rudder forwards then ticking over in reverse. Could turn the boat in not much more space than the boat length, but may not track as well, may slam more, and make more leeway.
