Footloose replied:

There is little difference in performance between the two. The f/g one will tune down to 2020khz, but the stainess one might not.

Tony MD replied:

Being longer, the fiberglass whip will be slightly more efficient than the shorter stainless steel whip - & more so with the spring fitted. The shorter whip probably wont tune on the low RFDS frequencies such as 2020khz. I doubt that you will be able to tell much difference!
The fiberglass whip, being more rigid, will provide better performance whilst mobile - less mobile flutter.
The short whip is handy to use where height clearance is a problem.
Efficiency of the 9350 auto tune antenna can be radically improved by extending the whip (can be done at the spring) by slightly less than a 1/4 wave length using wire - doesn't have to be vertical or straight. This improves the radiation efficiency & losses in the matching section. Only to be done whilst stationary.
Happy new year, Tony.

Mike replied:

Hi Tony I have the same set up as you, I also have the fibre glass aerial, a SS 1.8m and a SS1.6m I use the SS 1.6m all the time I havent noticed any difference when I have changed aerials during a sked to try them out, as the others have said you wont be able to tune into RFDS 2020 with the SS whips. all the best, Whisky 1244