I say for me it´s based on time.
On 3 on my figurenes, i spent about 400 hours on them.
My main one which is Silent Sinner in this case, it´s over 1000 hours.
Really, in the beginning i had a male Cast named Darkante which is supposed to resembled me...but then i feelt the sudden urge to change over.
SS took his place...for some reason i were in a other thinking mode making that Male Cast again.
His Name is in Swedish.
[PSO2] Darkante: Cast HU-44/RA-43/FI-42/GU-30
Astral Storm: Newman F HU-35
RB3 - Dark Knight "Ante" : Cast M Lv 177/ JLv Hu50/Ra50/Fo1/Va46
RB3 - Crimson Sky: Beast F Lv 124/ JLv Hu32/Ra18/Fo1/Va50
RB0 - Zone Dynamite: Beast M Lv 76/ JLv Hu0/Ra7/Fo0/Va0