Cost is one factor...but Tangenital arms or linear tracking arms have their own set of problems. It is very difficult and expensive to get a linear tracking arm to be completely "friction" free which is one of the prinicple advantages of these arms as well as the tracing geometry that is more suited to the cutting lathe. Linear arms use either a type of air bearing or electric servo to help them track the groove of the record. The old Rabco arm was a popular arm in its day..but had enough internal resonance to be a factor on the better tables. Walkers air bearing linear arm is state of the art today..but the arm alone costs more than some complete analog set ups..So, it mainly comes down to being able to design a linear arm thats up to snuff and yet compete with the more popular pivoted designs out there today, which are quite good in themselves!
As SdCampbell mentioned..the longer 12" arms provide less tracking error due to their shallower offset..but many tables with compact plinths and armboards cannot acccept that size. If you can though, it may be worthwhile to go with the 12"
As SdCampbell mentioned..the longer 12" arms provide less tracking error due to their shallower offset..but many tables with compact plinths and armboards cannot acccept that size. If you can though, it may be worthwhile to go with the 12"