davefr,
The antenna in Access is a coiled shortened vertical. It is omni-directional, resonant, and impedance matched to the radio. In my view it does a much better job than the bent wire strung around the smartHUB. I see more consistent performance with less sensitivity to sensor placement. Others have reported seeing higher signal strengths vs. the hub, or seeing neighborhood devices they did not previously detect.
One other observation, though. Access seems to require a bit more distance from a router or other WiFi sources. In my setup, getting too close has resulted in unstable signal strengths reported for my sensors.