Tone arm length

@mikelavigne Thank you for the thoughtful insight. That makes a lot of sense.

What little I know about this, the benefits of the longer arm (#3) apply mostly to the inner grooves.   

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.

@OP. One logistical issue to consider is that the 12inch arm has a bigger footprint due to the longer cantilever mounting plate

As regards sound quality, be sure to consider the Professional PSU. Versus the standard wall wart PSU, this will make a much bigger difference than any differences between the two arm lengths.

The Universal is a superb arm and you won't feel short changed in sound quality which ever length you specify.

Go Big or Go Home.....12 in.    .all the way. But have a professional set it up.

@yoyoyaya thanks for the feedback. The professional power supply is only compatible with concept and performance TT according to their website.

im curious how the PS improves sound if TT speed is optically controlled and the motor is decoupled from the platter?