I would urge you to also consider the distributor you are buying your
instrument from. The installation, calibration, and maintenance from
this distributor is another "feature" you'll have to live with.
I don't know the geography of Montana or where you'll practice, but
another consideration should be can these manufacturers/distributors get
service or loaner equipment to you when you need it. Also if you'll be
using sound field, who can perform that calibration least expensively.
The GSI 16 is a good instrument with a long history of good performance.
The only fault I have found with the instrument is that it often requires
a new display circuit board eventually as the display will fade over time
to become unreadable.
The Madsen Orbiter is a very new unit and I know of no one currently
using one. I believe, however, that the unit can be connected via RS-232
cable to a computer, and software is available to also connect that
computer to a Frye Real Ear system. The software then allows all
information from both instruments to be combined and manipulated.
Note: I am a medical instrument repairman working primarily with audio
instrumentation. GSI and Madsen are not my manufacturers, so I think my
opinion is unbiased.