What have you finally decided? After reading this post and recognizing a similar need for a road bike, I purchased the AKM 75SX with a 14.6 ratio, hoping for good freewheeling performance. However, when testing it by hand (it's not yet mounted on a wheel rim), I noticed that while the freewheel side does roll easily, it doesn't maintain momentum at all and stops immediately. I asked the seller, and they confirmed that it's normal for the motor to have some resistance.
Hoping this isn't like the xiongda motor,maybe somebody can confirm its results with this one?