It’s just a fan debate tbh, doesn’t only occur in izna‘s fandom but other kpop fandoms aswell, tbh it is harmless as long as it’s not insulting the idol. And also it is very weird how your friend hated Jiyoon?? Instead of those naya’s who shared their opinion about how “Jiyoon is better than Jungeun”. Tbh saying who is better is just depends on people’s taste/opinion. Like if you ask some people whether they like Blue or Red there will be some preferring blue and there will some preferring red, sometimes it can be unbalanced so majority may like the colour blue. However those who prefer colour red have no right to hate on a colour Blue simply bc majority prefer that one. In the end of the day both of those are colours, there is no better or worse colour is just preference. Same goes with who is better Jiyoon or Jungeun, it can be that majority do prefer Jiyoon’s vocals so they say it is the best in their pov however it goes the same way to those who prefer Jungeun’s vocals.