I think something else you may have to consider is the control scheme.
If you go realistic, you'll frustrate many people. From what i've heard, flying a helicopter is an exercise in frustration much like learning to pat your head whilst rubbing your stomach and whistling a tune if you can't already naturally do these three things at once.
I've only ever really had experience of helicopters in 'realistic' flight sims such as X-Plane and FlightGear. In these, it was so annoying that I gave up. I have however flown both simulated planes and a real plane and these were easy to get to grips with in both situations.
My thought: beyond the dynamics and simulation, regardless of whether you choose to have a realistic sim or not, please please don't choose realistic control schemes unless you want to severely limit your game's audience. Just my $0.02 worth.