You have to measure what each group did in their era.
And what SNSD did in 2nd gen is far more impressive than what Twice did in 3rd gen. Of course Twice is bigger overall. That's what happens when you debut in 2015 instead of 2007.
Twice debuted at the tail end of the golden age of girl groups. That's like a 5 minute head start when compared to SNSD debuting in 2007. This was the worst era of girl groups in history because basically there was no girl groups prior to this. 2003 to 2006 was almost the "No girls allowed " era.
But WonSoKa changed EVERYTHING in 2007 and SNSD eventually emerged the Champion of Champions. We are talking about a girl group that was battling TVXQ, SuJu, BigBang, and even a prime IU and coming out on top.
This is the equivalent of Twice beating BTS, EXO, Seventeen and Blackpink. But that never happened.
Remember SNSD was so huge in Korea they put them on the Olympics brochure in 2018 instead of Twice or BTS when both those groups were in their prime.
The reason we even have girl groups today is because of SNSD.
I can't believe I still have to make this thread in 2023.