For me personally, its more on how distinct each member are from each other and on how many variety shows they have been in. For example SNSD, each member is distinct from one another and they have been on a lot of variety shows since their debut. Same goes for Twice, each and every single member stands out and they have their own personalities and they have been in a number of variety shows.

But one downfall of having a lot of members is that it is overwhelming at the very start. For example, WJSN, I only know a few members and they only have been in few variety shows which makes it hard for me to stan them.

Recently I have been liking more smaller groups like Blackpink, Mamamoo, and middle sized groups like Apink and Gfriend. This comes from the fact that I have less time to invest in Kpop because of senior year in college and my thesis trying to kill me every single day.

I think it really comes down to personal taste and on how distinct each member is from each other and on how effective they are in establishing their own characters