Plane - Heli
Nrgy
400 NM is feasible with the heli only. Taking the math above: 2.5Hrs versus 3.6+0.4=4.0hrs, boils down to how long will you spend going up and down to the airports (times two), unless you can land the plane at the location.
One draw back of the heli is that you need to refill, which could create planning problems.
Also figure that with the plane option you will need more than 1 heli, or an extra pilot that flies the heli.
d3