You are confusing the baud rate ( 9600 ) with the data packet rate (10 ).
The baud rate allows up to 9600 bits per second ( ~950 bytes per second ). But, the wideband only sends 10 sample packets per second. So, there is some space in-between. It's slow enough that you can watch them scroll by on the hyperterm screen. It is this slow, only, because it was supposed to be compatible with the older 30-4100 and 30-2310 devices; which, did not have CAN output. And, really weren't any faster than that anyway.
Additionally, the serial data is only 3-digits. "xx.x" So, there is nothing between 14.7 and 14.8, for example. It's really just a vestigial feature; to allow AEM to phase out the older models, without leaving old ECUs that rely on it, out in the cold.
The analog data is updated 500 times / second. So, it is, literally, 50X faster than the serial data.
And, it has the full 10-bit resolution. IIRC it steps from 14.7 to 14.72, etc.
Here is a trace on the analog output. Going from free-air to 14.7AFR
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You can see the steps 2ms apart. Even the CAN data only updates every 10ms. Which is one of those dividing lines.
I would never use the serial data over the analog data on the 30-03xx, unless I had to.