What are the pros and cons of each?
To me it looks like a coax would be better for a small helicopter because the torque effect is cancelled out and you dont need a tail rotor.

I totally love that Schimede or whatever its called.
When it came out I asked Hilly same question, apparently not all are created equally.
Some coax helis don't or can't auto rotate!
At least thats the part that stuck with me.
I might have that wrong though.

Ask yourselves why there isn't more of them?

1. coaxial torque is = but you lose directional control or suffer control reversal in yaw in autorotation or low power.*
2. higher cost in main blades and controls
3. higher gearbox weight
4. Blade collision with abrupt maneuvers and limited speed unless ridged hub

More helicopter are conventional - Easier to fly - No node points in flight envelope (positive yaw control)

* See the Gyrodyne QH 50 and RON 1 - The only coaxial with positive yaw control in any flight maneuver

With a single rotor you build only one set of blades, one hub etc, A small tail rotor with it's gear box costs less.
and manufacture is about cost - mission profile - maintenance costs - parts cost. A coaxial has a higher cost to build.

If you want dual rotors try tandem like a Chinook, Wider c/g, faster, simple controls

Thanks for the info,
This is intersting.
[Youtube]f1kO1ZBEXFc&t=14s[/Youtube]