[aprssig] 1200 vs 9600 baud (was: Tracker3 9600 baud balloon tracker beta offer)

[Ted11]

Scott's balloon tracker has gotten me thinking again about a lingering
question, 1200 vs 9600 baud for APRS.  I think I understand this:

1.  9600 lets you send more data per time interval. 
2.  9600 requires tighter radio integration (can't just plug into the
microphone jack).
3.  9600 seems to work best (only?) on UHF.

Beyond those rather rudimentary constraints, I'm not sure how to decide to
use 1200 or 9600.  All my APRS stuff so far is done at 1200, but I'm
interested in what advantages 9600 might have.  So how would you answer the
question, "When should I use 9600 baud for APRS and when should I use 1200
baud?"

Thanks.

Ted
K5KZ