Another factor to consider is the effective moving mass of each length. I don't know how much emm the 3" adds, but the lower a cartridge's compliance is, the more it "likes" a higher emm arm. And of course the inverse is also true.
Tone arm length
I assume this question is not brand specific.
However my question is specifically related to the Clearaudio Innovation Wood with the Universal tonearm, 9 or 12" options. The cost between the two is minimal, but I'd love to hear opinions on why one or the other is preferred.
Thank you.