Hi,
I have both.
The Ambient measures wind speed/gust at least every second (although it displays it ever 4 seconds). It uses the collection of reading in that 4 second period and averages it out to determine what it displays. The ambient saves the maximum of these (<1 second ) second reading to determine the MAX Daily Gust.
The Tempest displays the wind every 3 seconds and I think uses it to save the max wind as the gust.
As a result, the Ambient will catch short term "mico gusts" where the tempest does not.
Since I live in a gusty environment with a fair amount of trees.. I prefer the ambient.
Also... I have not seen false max wind readings like I used to see on the tempest. I think they got rid of those via software updates.
Hope that helps.