Bill: I'm not sure what "performance" measure we're really discussing here. Are we talking about the power of the tail itself or the liveliness of the gyro's performance (climb rate, top speed, etc.)?
A pusher gyro (or pusher airplane, for that matter) is stuck with a short tail arm. For a given number of pounds of force created by the tail feathers, the actual moment on the aircraft becomes less and less as the tail arm gets shorter.
To combat this problem, one can make the tail feathers larger, of course. At some point, this tactic become impractical.
An additional problem specific to gyro tail feathers is that the aircraft can be operated at low-to-zero airspeeds. No matter how big your tail feathers, they will not generate any forces at zero airspeed. Yet, a gyro with any amount of high thrustline (HTL) must have horizontal surfaces that can generate stabilizing moments on the frame at zero MPH. Since we don't have a tail rotor, we also need vertical control surfaces that still work at zero MPH.
The normal solution to these problems is to immerse the tail in the propwash. You can see this tactic employed on pusher amphibs such as the Aircar/Seabee, Lake Amphib and many others, not to mention the original pusher gyro, the Buhl Autogiro of the 1930's.
It's not really a question of what provides the aircraft with the hottest performance. Rather, it's what will keep it from being unstable and/or uncontrollable at low speeds. Tail immersion is not a performance-enhancer, it's a matter of survival.
If OTOH the issue is that the propwash supposedly "overwhelms" the freestream flow and continues to blow in the same direction over the tail, no matter what direction the freestream flow comes from, this is simply untrue. The propwash direction is profoundly influenced by the orientation of the flow INTO the prop disk. The propwash moves around as the inflow does. This fact has been discussed extensively here in the past. It can easily be proven by using a pair of electric fans with yarn tufts tied to their grilles.