Elliot, I have a 9" arm and a 14" arm. It all depends on the cartridge. I put stiff cartridges like the Koetsu and the Air Tight in the long arm. I put softer cartridges like the Lyra, Windfeld Ti and Clearaudio in the 9" arm.
I can't say one sounds better than the other. They sound different probably mostly due to the cartridges. The differences are surprisingly subtle. I can say that I have never heard a Koetsu do bass or sound punchier than it does in the Kuzma 4 point 14. I have a Rosewood Signature Platinum because it weights a lot less than one of the stone models which would push the effective mass over the edge. The Koetsu RSP and 14" Kuzma are a match made in heaven. The Windfeld Ti in the 4 point 9" will track anything you throw at it. It beats all the others in tracking tests. If I were to use just one arm I would get an SME V 12. It is a very light 12" arm and with the addition of head shell weights would be able to accommodate any modern cartridge. I like the 4 point 9 a lot but the reason I have it is that the SOTA will only take 9 to 10" arms. The Tri Planar arms are also excellent.
I can't say one sounds better than the other. They sound different probably mostly due to the cartridges. The differences are surprisingly subtle. I can say that I have never heard a Koetsu do bass or sound punchier than it does in the Kuzma 4 point 14. I have a Rosewood Signature Platinum because it weights a lot less than one of the stone models which would push the effective mass over the edge. The Koetsu RSP and 14" Kuzma are a match made in heaven. The Windfeld Ti in the 4 point 9" will track anything you throw at it. It beats all the others in tracking tests. If I were to use just one arm I would get an SME V 12. It is a very light 12" arm and with the addition of head shell weights would be able to accommodate any modern cartridge. I like the 4 point 9 a lot but the reason I have it is that the SOTA will only take 9 to 10" arms. The Tri Planar arms are also excellent.