In theory, the arm should be completely neutral it what it does. It's rare that you can get a chance to directly compare different arms on the same table in the same system using the same cartridge (arguably, there are cartridge to cartridge variations among the same model from the same manufacturer). Rigidity is another factor, which is partly materials and partly design.

I use it only to really dial in the arm by ear once it is level and otherwise in alignment. There are also other considerations in the design including the type and quality of the bearings, whether the arm allows on the fly (while you are playing) VTA (height) adjustment - a factor that is more important to some than others. With straight tonearms, this offset angle will need to be included which removes the ability to be standardized. The advantage of this is that a standardized removeable headshell can be used. On a J or S shaped tonearm the offset angle is incorporated into the geometry of the shaft, which allows for straight slots in headshell. With a straight tonearm the headshell slots will be angled. The headshell will generally incorporate an offset angle where the stylus is precisely tangent at the null points. There is one advantage if the use of a removable headshell is incorporated with an S or J shaped arm. Again this isn't an advantage, it's just a design parameter. But an S-shaped arm will have more effective mass than a straight arm made of similar materials and construction. This is obvious on a straight arm, but on an S or J shaped arm, the path of the effective length cuts through air. The effective length is the distance between the pivot and the stylus tip. All tonearms are bound by the travel along the effective length. Which means there is less deviation in the tracking angle from precisely parallel outside of the null points.

Sme tonearm length