Dear @mijostyn : you are rigth, the 12" against a 10" EL tonearm in reality makes almost insignificant " improve " in tracking error. Using Löfgren A alignment IEC:
high tracking error in 12" is 1.4° at 146mm ( outer groove) and from 120mm. to 66mm is 0°and at most inner groove ( 60mm ) is 0.56°
in the 10" is 1.65° at most outer groove and 0° from 119mm to 66mm and at most inner groove is 0.57°
All those with 100% accuracy in the alignment but any tiny inaccuracy in the alignment makes that the 12" error gone way higher than in a short tonearm.
Nothing justify a longer tonearm other that the " no sense ": " I like it " or just ignorance. In the other side a longer tonearm develops higher resonances/vibrations/self distortions ( everything the same. ).
R.